diff --git a/mailnews/base/test/unit/test_imapPump.js b/mailnews/base/test/unit/test_imapPump.js
index 61d33053c4..e93c15b140 100644
--- a/mailnews/base/test/unit/test_imapPump.js
+++ b/mailnews/base/test/unit/test_imapPump.js
@@ -39,14 +39,14 @@ var gTestArray =
   },
 
   // the main test
-  function* loadImapMessage()
+  async function loadImapMessage()
   {
     IMAPPump.mailbox.addMessage(
       new imapMessage(specForFileName(gMessage),
                       IMAPPump.mailbox.uidnext++, []));
     let promiseUrlListener = new PromiseTestUtils.PromiseUrlListener();
     IMAPPump.inbox.updateFolderWithListener(gDummyMsgWindow, promiseUrlListener);
-    yield promiseUrlListener.promise;
+    await promiseUrlListener.promise;
 
     Assert.equal(1, IMAPPump.inbox.getTotalMessages(false));
     let msgHdr = mailTestUtils.firstMsgHdr(IMAPPump.inbox);
diff --git a/mailnews/base/test/unit/test_searchChaining.js b/mailnews/base/test/unit/test_searchChaining.js
index 0d7c6f47bc..50414628ce 100644
--- a/mailnews/base/test/unit/test_searchChaining.js
+++ b/mailnews/base/test/unit/test_searchChaining.js
@@ -15,7 +15,7 @@ ChromeUtils.import("resource://testing-common/mailnews/IMAPpump.js");
 ChromeUtils.import("resource://testing-common/mailnews/imapd.js");
 ChromeUtils.import("resource://testing-common/mailnews/PromiseTestUtils.jsm");
 
-function *setupFolder()
+async function setupFolder()
 {
   // add a single message to the imap inbox.
   let messages = [];
@@ -32,10 +32,10 @@ function *setupFolder()
   // update folder to download header.
   let listener = new PromiseTestUtils.PromiseUrlListener();
   IMAPPump.inbox.updateFolderWithListener(null, listener);
-  yield listener.promise;
+  await listener.promise;
 }
 
-function *searchTest()
+async function searchTest()
 {
   // Get the IMAP inbox...
   var emptyLocal1 = localAccountUtils.rootFolder.createLocalSubfolder("empty 1");
@@ -51,11 +51,11 @@ function *searchTest()
   let listener = new PromiseTestUtils.PromiseSearchNotify(
                        searchSession, searchListener);
   searchSession.search(null);
-  yield listener.promise;
+  await listener.promise;
 
   // After the search completes, there still seem to be active URLs, so we
   //   have to wait before we are done and clear.
-  yield PromiseTestUtils.promiseDelay(1000);
+  await PromiseTestUtils.promiseDelay(1000);
 }
 
 // nsIMsgSearchNotify implementation
diff --git a/mailnews/compose/test/unit/test_attachment.js b/mailnews/compose/test/unit/test_attachment.js
index 932baf499e..26df45aaea 100644
--- a/mailnews/compose/test/unit/test_attachment.js
+++ b/mailnews/compose/test/unit/test_attachment.js
@@ -110,18 +110,18 @@ function checkAttachment(expectedCD, expectedCT) {
   Assert.equal(contentType, expectedCT);
 }
 
-function* testInput0() {
+async function testInput0() {
   for (let folding in ParamFoldingPref) {
     Services.prefs.setIntPref("mail.strictly_mime.parm_folding", ParamFoldingPref[folding]);
-    yield createMessage(input0);
+    await createMessage(input0);
     checkAttachment(expectedCD0, expectedCTList0[folding]);
   }
 }
 
-function* testInput1() {
+async function testInput1() {
   for (let folding in ParamFoldingPref) {
     Services.prefs.setIntPref("mail.strictly_mime.parm_folding", ParamFoldingPref[folding]);
-    yield createMessage(input1);
+    await createMessage(input1);
     checkAttachment(expectedCD1, expectedCTList1[folding]);
   }
 }
diff --git a/mailnews/compose/test/unit/test_bug155172.js b/mailnews/compose/test/unit/test_bug155172.js
index d9f3f2c420..7d85933f27 100644
--- a/mailnews/compose/test/unit/test_bug155172.js
+++ b/mailnews/compose/test/unit/test_bug155172.js
@@ -33,7 +33,7 @@ var kUsername = "test.smtp@fakeserver";
 var kPassword1 = "wrong";
 var kPassword2 = "smtptest";
 
-add_task(function *() {
+add_task(async function () {
   registerAlertTestUtils();
 
   function createHandler(d) {
@@ -51,7 +51,7 @@ add_task(function *() {
   server.setDebugLevel(fsDebugAll);
 
   // Prepare files for passwords (generated by a script in bug 1018624).
-  yield setupForPassword("signons-smtp.json");
+  await setupForPassword("signons-smtp.json");
 
   // Test file
   var testFile = do_get_file("data/message1.eml");
diff --git a/mailnews/compose/test/unit/test_detectAttachmentCharset.js b/mailnews/compose/test/unit/test_detectAttachmentCharset.js
index b4fc9637bd..03e93ddad8 100644
--- a/mailnews/compose/test/unit/test_detectAttachmentCharset.js
+++ b/mailnews/compose/test/unit/test_detectAttachmentCharset.js
@@ -23,23 +23,23 @@ function getContentCharset(aContent) {
   return null;
 }
 
-function *testUTF8() {
-  yield createMessage(do_get_file("data/test-UTF-8.txt"));
+async function testUTF8() {
+  await createMessage(do_get_file("data/test-UTF-8.txt"));
   checkAttachmentCharset("UTF-8");
 }
 
-function *testUTF16BE() {
-  yield createMessage(do_get_file("data/test-UTF-16BE.txt"));
+async function testUTF16BE() {
+  await createMessage(do_get_file("data/test-UTF-16BE.txt"));
   checkAttachmentCharset("UTF-16BE");
 }
 
-function *testUTF16LE() {
-  yield createMessage(do_get_file("data/test-UTF-16LE.txt"));
+async function testUTF16LE() {
+  await createMessage(do_get_file("data/test-UTF-16LE.txt"));
   checkAttachmentCharset("UTF-16LE");
 }
 
-function *testShiftJIS() {
-  yield createMessage(do_get_file("data/test-SHIFT_JIS.txt"));
+async function testShiftJIS() {
+  await createMessage(do_get_file("data/test-SHIFT_JIS.txt"));
   checkAttachmentCharset(null); // do not detect SHIFT_JIS in this file anymore
 }
 
diff --git a/mailnews/compose/test/unit/test_longLines.js b/mailnews/compose/test/unit/test_longLines.js
index 01409df37f..c6a404997a 100644
--- a/mailnews/compose/test/unit/test_longLines.js
+++ b/mailnews/compose/test/unit/test_longLines.js
@@ -84,7 +84,7 @@ let longMultibyteLineCJK = "안".repeat(400);
 // And some Japanese.
 let longMultibyteLineJapanese = "語".repeat(450);
 
-function* testBodyWithLongLine() {
+async function testBodyWithLongLine() {
   let newline;
   // Windows uses CR+LF, the other platforms just LF.
   // Note: Services.appinfo.OS returns "XPCShell" in the test, so we
@@ -108,7 +108,7 @@ function* testBodyWithLongLine() {
     "<meta http-equiv=\"content-type\" content=\"text/html; charset=utf-8\">" +
     "</head><body>" + longMultibyteLine + "</body></html>";
   fields.body = htmlMessage;
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeadersAndBody(
     {
       "Content-Type": "text/html; charset=UTF-8",
@@ -121,7 +121,7 @@ function* testBodyWithLongLine() {
   fields.body = htmlMessage;
   fields.forcePlainText = true;
   fields.useMultipartAlternative = false;
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeadersAndBody(
     {
       "Content-Type": "text/plain; charset=UTF-8; format=flowed",
@@ -136,7 +136,7 @@ function* testBodyWithLongLine() {
     "<meta http-equiv=\"content-type\" content=\"text/html; charset=utf-8\">" +
     "</head><body>" + longMultibyteLineCJK + "</body></html>";
   fields.body = htmlMessage;
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeadersAndBody(
     {
       "Content-Type": "text/html; charset=UTF-8",
@@ -149,7 +149,7 @@ function* testBodyWithLongLine() {
   fields.body = htmlMessage;
   fields.forcePlainText = true;
   fields.useMultipartAlternative = false;
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeadersAndBody(
     {
       "Content-Type": "text/plain; charset=UTF-8; format=flowed",
@@ -166,7 +166,7 @@ function* testBodyWithLongLine() {
     "<meta http-equiv=\"content-type\" content=\"text/html; charset=ISO-2022-JP\">" +
     "</head><body>" + longMultibyteLineJapanese + "</body></html>";
   fields.body = htmlMessage;
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeadersAndBody(
     {
       "Content-Type": "text/html; charset=ISO-2022-JP",
@@ -180,7 +180,7 @@ function* testBodyWithLongLine() {
   fields.body = htmlMessage;
   fields.forcePlainText = true;
   fields.useMultipartAlternative = false;
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
 
   // Expected body: The message without the tags and chopped up in
   // chunks of 36 characters with a space appended to each line.
@@ -205,7 +205,7 @@ function* testBodyWithLongLine() {
   fields.body = htmlMessage;
   Services.prefs.setBoolPref("mailnews.send_plaintext_flowed", false);
 
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeadersAndBody(
     {
       "Content-Type": "text/plain; charset=ISO-2022-JP",
diff --git a/mailnews/compose/test/unit/test_messageHeaders.js b/mailnews/compose/test/unit/test_messageHeaders.js
index 41933d47aa..08ae8235f0 100644
--- a/mailnews/compose/test/unit/test_messageHeaders.js
+++ b/mailnews/compose/test/unit/test_messageHeaders.js
@@ -77,7 +77,7 @@ function checkMessageHeaders(msgData, expectedHeaders, partNum = "") {
   Assert.ok(seen);
 }
 
-function* testEnvelope() {
+async function testEnvelope() {
   let fields = new CompFields();
   let identity = getSmtpIdentity("from@tinderbox.invalid",
     getBasicSmtpServer());
@@ -90,7 +90,7 @@ function* testEnvelope() {
   fields.replyTo = "Charles <charles@tinderbox.invalid>";
   fields.organization = "World Salvation Committee";
   fields.subject = "This is an obscure reference";
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeaders({
     // As of bug 87987, the identity does not override the from header.
     "From": "Nobody <nobody@tinderbox.invalid>",
@@ -104,7 +104,7 @@ function* testEnvelope() {
   });
 }
 
-function* testI18NEnvelope() {
+async function testI18NEnvelope() {
   let fields = new CompFields();
   let identity = getSmtpIdentity("from@tinderbox.invalid",
     getBasicSmtpServer());
@@ -115,7 +115,7 @@ function* testI18NEnvelope() {
   fields.bcc = "Étienne <boris@tinderbox.invalid>";
   fields.replyTo = "Frédéric <charles@tinderbox.invalid>";
   fields.subject = "Ceci n'est pas un référence obscure";
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeaders({
     "From": "=?UTF-8?B?44Kx44OE44Kh44Or44Kz44Ki44OI44Or?= <from@tinderbox.invalid>",
     "Organization": "=?UTF-8?Q?Comit=c3=a9_de_la_destruction_du_monde?=",
@@ -127,7 +127,7 @@ function* testI18NEnvelope() {
   });
 }
 
-function* testIDNEnvelope() {
+async function testIDNEnvelope() {
   let fields = new CompFields();
   let domain = "ケツァルコアトル.invalid";
   // We match against rawHeaderText, so we need to encode the string as a binary
@@ -142,7 +142,7 @@ function* testIDNEnvelope() {
   fields.bcc = "Boris <boris@" + domain + ">";
   fields.replyTo = "Charles <charles@" + domain + ">";
   fields.subject = "This is an obscure reference";
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeaders({
     // The identity sets the from field here.
     "From": "from@tinderbox.invalid",
@@ -154,11 +154,11 @@ function* testIDNEnvelope() {
   });
 }
 
-function* testDraftInfo() {
+async function testDraftInfo() {
   let fields = new CompFields();
   let identity = getSmtpIdentity("from@tinderbox.invalid",
     getBasicSmtpServer());
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeaders({
     "FCC": identity.fccFolder,
     "X-Identity-Key": identity.key,
@@ -167,42 +167,42 @@ function* testDraftInfo() {
   });
 
   fields.attachVCard = true;
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeaders({
     "X-Mozilla-Draft-Info": "internal/draft; " +
       "vcard=1; receipt=0; DSN=0; uuencode=0; attachmentreminder=0; deliveryformat=4",
   });
 
   fields.returnReceipt = true;
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeaders({
     "X-Mozilla-Draft-Info": "internal/draft; " +
       "vcard=1; receipt=1; DSN=0; uuencode=0; attachmentreminder=0; deliveryformat=4",
   });
 
   fields.DSN = true;
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeaders({
     "X-Mozilla-Draft-Info": "internal/draft; " +
       "vcard=1; receipt=1; DSN=1; uuencode=0; attachmentreminder=0; deliveryformat=4",
   });
 
   fields.attachmentReminder = true;
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeaders({
     "X-Mozilla-Draft-Info": "internal/draft; " +
       "vcard=1; receipt=1; DSN=1; uuencode=0; attachmentreminder=1; deliveryformat=4",
   });
 
   fields.deliveryFormat = Ci.nsIMsgCompSendFormat.Both;
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeaders({
     "X-Mozilla-Draft-Info": "internal/draft; " +
       "vcard=1; receipt=1; DSN=1; uuencode=0; attachmentreminder=1; deliveryformat=3",
   });
 }
 
-function* testOtherHeaders() {
+async function testOtherHeaders() {
   let fields = new CompFields();
   let identity = getSmtpIdentity("from@tinderbox.invalid",
     getBasicSmtpServer());
@@ -210,7 +210,7 @@ function* testOtherHeaders() {
   fields.references = "<fake@tinderbox.invalid> <more@test.invalid>";
   fields.setHeader("X-Fake-Header", "124");
   let before = Date.now();
-  let msgHdr = yield richCreateMessage(fields, [], identity);
+  let msgHdr = await richCreateMessage(fields, [], identity);
   let after = Date.now();
   let msgData = mailTestUtils.loadMessageToString(msgHdr.folder, msgHdr);
   checkMessageHeaders(msgData, {
@@ -256,14 +256,14 @@ function* testOtherHeaders() {
   let expected = references.slice(47);
   expected.unshift(references[0]);
   fields.references = references.join(" ");
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeaders({
     "References": expected.join(" "),
     "In-Reply-To": references[references.length - 1],
   });
 }
 
-function* testNewsgroups() {
+async function testNewsgroups() {
   let fields = new CompFields();
   let nntpServer = localAccountUtils.create_incoming_server("nntp", 534,
       "", "");
@@ -273,7 +273,7 @@ function* testNewsgroups() {
     getBasicSmtpServer());
   fields.newsgroups = "mozilla.test, mozilla.test.multimedia";
   fields.followupTo = "mozilla.test";
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeaders({
     // The identity should override the compose fields here.
     "Newsgroups": "mozilla.test,mozilla.test.multimedia",
@@ -282,7 +282,7 @@ function* testNewsgroups() {
   });
 }
 
-function* testSendHeaders() {
+async function testSendHeaders() {
   let fields = new CompFields();
   let identity = getSmtpIdentity("from@tinderbox.invalid",
     getBasicSmtpServer());
@@ -294,7 +294,7 @@ function* testSendHeaders() {
     "replyto@test.invalid");
   fields.to = "list@test.invalid";
   fields.cc = "not-list@test.invalid";
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeaders({
     "X-Custom-1": "A header value",
     "X-Custom-2": "=?UTF-8?Q?_Enchant=c3=a9?=",
@@ -305,7 +305,7 @@ function* testSendHeaders() {
   // Don't set the M-F-T header if there's no list.
   fields.to = "replyto@test.invalid";
   fields.cc = "";
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeaders({
     "X-Custom-1": "A header value",
     "X-Custom-2": "=?UTF-8?Q?_Enchant=c3=a9?=",
@@ -314,14 +314,14 @@ function* testSendHeaders() {
   });
 }
 
-function* testContentHeaders() {
+async function testContentHeaders() {
   // Disable RFC 2047 fallback
   Services.prefs.setIntPref("mail.strictly_mime.parm_folding", 2);
   let fields = new CompFields();
   fields.body = "A body";
   let identity = getSmtpIdentity("from@tinderbox.invalid",
     getBasicSmtpServer());
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeaders({
     "Content-Type": "text/html; charset=UTF-8",
     "Content-Transfer-Encoding": "7bit"
@@ -329,7 +329,7 @@ function* testContentHeaders() {
 
   // non-ASCII body should be 8-bit...
   fields.body = "Archæologist";
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeaders({
     "Content-Type": "text/html; charset=UTF-8",
     "Content-Transfer-Encoding": "8bit"
@@ -338,7 +338,7 @@ function* testContentHeaders() {
   // What if we change the message charset?
   fields.characterSet = "ISO-8859-1";
   fields.body = "Archæologist";
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeaders({
     "Content-Type": "text/html; charset=ISO-8859-1",
     "Content-Transfer-Encoding": "8bit"
@@ -355,7 +355,7 @@ function* testContentHeaders() {
     "Content-Transfer-Encoding": "base64",
     "Content-Disposition": "attachment; filename=\"attachment.txt\"",
   };
-  yield richCreateMessage(fields, [plainAttachment], identity);
+  await richCreateMessage(fields, [plainAttachment], identity);
   checkDraftHeaders({
     "Content-Type": "text/html; charset=ISO-8859-1",
     "Content-Transfer-Encoding": "7bit"
@@ -365,13 +365,13 @@ function* testContentHeaders() {
   plainAttachment.name = "oïl.txt";
   plainAttachmentHeaders["Content-Disposition"] =
     "attachment; filename*=ISO-8859-1''%6F%EF%6C%2E%74%78%74";
-  yield richCreateMessage(fields, [plainAttachment], identity);
+  await richCreateMessage(fields, [plainAttachment], identity);
   checkDraftHeaders(plainAttachmentHeaders, "2");
 
   plainAttachment.name = "\ud83d\udca9.txt";
   plainAttachmentHeaders["Content-Disposition"] =
     "attachment; filename*=UTF-8''%F0%9F%92%A9%2E%74%78%74";
-  yield richCreateMessage(fields, [plainAttachment], identity);
+  await richCreateMessage(fields, [plainAttachment], identity);
   checkDraftHeaders(plainAttachmentHeaders, "2");
 
   let httpAttachment = makeAttachment({
@@ -384,7 +384,7 @@ function* testContentHeaders() {
     "Content-Base": '"data:text/html,<html></html>"',
     "Content-Location": '"data:text/html,<html></html>"',
   };
-  yield richCreateMessage(fields, [httpAttachment], identity);
+  await richCreateMessage(fields, [httpAttachment], identity);
   checkDraftHeaders({
     "Content-Base": undefined,
     "Content-Location": undefined
@@ -405,14 +405,14 @@ function* testContentHeaders() {
       "provider=akey; " +
       "file=" + cloudAttachment.url + "; name=attachment.html",
   };
-  yield richCreateMessage(fields, [cloudAttachment], identity);
+  await richCreateMessage(fields, [cloudAttachment], identity);
   checkDraftHeaders(cloudAttachmentHeaders, "2");
 
   // Some multipart/alternative tests.
   fields.body = "Some text";
   fields.forcePlainText = false;
   fields.useMultipartAlternative = true;
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeaders({
     "Content-Type": "multipart/alternative; boundary=."
   });
@@ -430,7 +430,7 @@ function* testContentHeaders() {
   //   + text/plain
   //   + text/html
   // + text/plain attachment
-  yield richCreateMessage(fields, [plainAttachment], identity);
+  await richCreateMessage(fields, [plainAttachment], identity);
   checkDraftHeaders({
     "Content-Type": "multipart/mixed; boundary=."
   });
@@ -448,7 +448,7 @@ function* testContentHeaders() {
   checkDraftHeaders(plainAttachmentHeaders, "2");
 
   // Three attachments, and a multipart/alternative. Oh the humanity!
-  yield richCreateMessage(fields,
+  await richCreateMessage(fields,
     [plainAttachment, httpAttachment, cloudAttachment], identity);
   checkDraftHeaders({
     "Content-Type": "multipart/mixed; boundary=."
@@ -471,21 +471,21 @@ function* testContentHeaders() {
   // Test a request for plain text with text/html.
   fields.forcePlainText = true;
   fields.useMultipartAlternative = false;
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   checkDraftHeaders({
     "Content-Type": "text/plain; charset=UTF-8; format=flowed",
     "Content-Transfer-Encoding": "7bit"
   });
 }
 
-function* testSentMessage() {
+async function testSentMessage() {
   let server = setupServerDaemon();
   let daemon = server._daemon;
   server.start();
   try {
     let localserver = getBasicSmtpServer(server.port);
     let identity = getSmtpIdentity("test@tinderbox.invalid", localserver);
-    yield sendMessage({
+    await sendMessage({
       "to": "Nobody <nobody@tinderbox.invalid>",
       "cc": "Alex <alex@tinderbox.invalid>",
       "bcc": "Boris <boris@tinderbox.invalid>",
@@ -502,11 +502,11 @@ function* testSentMessage() {
       "X-Mozilla-Draft-Info": undefined,
       "Fcc": undefined
     });
-    yield sendMessage({"bcc": "Somebody <test@tinderbox.invalid"}, identity);
+    await sendMessage({"bcc": "Somebody <test@tinderbox.invalid"}, identity);
     checkMessageHeaders(daemon.post, {
       "To": "undisclosed-recipients: ;"
     });
-    yield sendMessage({
+    await sendMessage({
       "to": "Somebody <test@tinderbox.invalid>",
       "returnReceipt": true,
       "receiptHeaderType": Ci.nsIMsgMdnGenerator.eDntRrtType,
@@ -522,7 +522,7 @@ function* testSentMessage() {
       name: "attachment.html",
       contentLocation: "http://localhost.invalid/",
     });
-    yield sendMessage({to: "test@tinderbox.invalid"}, identity, {},
+    await sendMessage({to: "test@tinderbox.invalid"}, identity, {},
       [cloudAttachment]);
     checkMessageHeaders(daemon.post, {
       "Content-Type": "application/octet-stream",
diff --git a/mailnews/compose/test/unit/test_saveDraft.js b/mailnews/compose/test/unit/test_saveDraft.js
index b8ab59d9d0..34d4a0e075 100644
--- a/mailnews/compose/test/unit/test_saveDraft.js
+++ b/mailnews/compose/test/unit/test_saveDraft.js
@@ -3,8 +3,8 @@
  * Test suite for checking correctly saved as draft with unread.
  */
 
-add_task(function* checkDraft() {
-  yield createMessage();
+add_task(async function checkDraft() {
+  await createMessage();
   Assert.equal(gDraftFolder.getTotalMessages(false), 1);
   Assert.equal(gDraftFolder.getNumUnread(false), 1);
 });
diff --git a/mailnews/compose/test/unit/test_sendObserver.js b/mailnews/compose/test/unit/test_sendObserver.js
index 92824ba17e..be1a700eef 100644
--- a/mailnews/compose/test/unit/test_sendObserver.js
+++ b/mailnews/compose/test/unit/test_sendObserver.js
@@ -23,7 +23,7 @@ var observer = {
   }
 }
 
-add_task(function* testObserver() {
+add_task(async function testObserver() {
   let fields = new CompFields();
   let identity = getSmtpIdentity("from@tinderbox.invalid",
     getBasicSmtpServer());
@@ -32,13 +32,13 @@ add_task(function* testObserver() {
   fields.cc = "Alex <alex@tinderbox.invalid>";
   fields.subject = "Let's test the observer";
 
-  yield richCreateMessage(fields, [], identity);
+  await richCreateMessage(fields, [], identity);
   // observer data should have:
   // (no account), Ci.nsIMsgSend.nsMsgSaveAsDraft, identity.key
   Assert.equal(gData, ",4,id1");
 
   // Now try with an account
-  yield richCreateMessage(fields, [], identity, localAccountUtils.msgAccount);
+  await richCreateMessage(fields, [], identity, localAccountUtils.msgAccount);
   // observer data should have:
   // (local account key), Ci.nsIMsgSend.nsMsgSaveAsDraft, identity.key
   Assert.equal(gData, "account1,4,id1");
diff --git a/mailnews/compose/test/unit/test_smtpPassword.js b/mailnews/compose/test/unit/test_smtpPassword.js
index 581bf4da68..275ca8c12b 100644
--- a/mailnews/compose/test/unit/test_smtpPassword.js
+++ b/mailnews/compose/test/unit/test_smtpPassword.js
@@ -17,7 +17,7 @@ var kUsername = "testsmtp";
 // file.
 var kPassword = "smtptest";
 
-add_task(function *() {
+add_task(async function () {
   function createHandler(d) {
     var handler = new SMTP_RFC2821_handler(d);
     // Username needs to match the login information stored in the signons json
@@ -30,7 +30,7 @@ add_task(function *() {
   server = setupServerDaemon(createHandler);
 
   // Prepare files for passwords (generated by a script in bug 1018624).
-  yield setupForPassword("signons-mailnews1.8.json")
+  await setupForPassword("signons-mailnews1.8.json")
 
   // Test file
   var testFile = do_get_file("data/message1.eml");
diff --git a/mailnews/compose/test/unit/test_smtpPassword2.js b/mailnews/compose/test/unit/test_smtpPassword2.js
index 1a1e8a27f0..88f92a9c1a 100644
--- a/mailnews/compose/test/unit/test_smtpPassword2.js
+++ b/mailnews/compose/test/unit/test_smtpPassword2.js
@@ -13,9 +13,9 @@ var kProtocol = "smtp";
 var kHostname = "localhost";
 var kServerUrl = kProtocol + "://" + kHostname;
 
-add_task(function *() {
+add_task(async function () {
   // Prepare files for passwords (generated by a script in bug 1018624).
-  yield setupForPassword("signons-mailnews1.8-multiple.json")
+  await setupForPassword("signons-mailnews1.8-multiple.json")
 
   // Set up the basic accounts and folders.
   localAccountUtils.loadLocalMailAccount();
diff --git a/mailnews/compose/test/unit/test_smtpPasswordFailure1.js b/mailnews/compose/test/unit/test_smtpPasswordFailure1.js
index bdf59a5161..88023a2e3a 100644
--- a/mailnews/compose/test/unit/test_smtpPasswordFailure1.js
+++ b/mailnews/compose/test/unit/test_smtpPasswordFailure1.js
@@ -56,7 +56,7 @@ function confirmEx(aDialogTitle, aText, aButtonFlags, aButton0Title,
   }
 }
 
-add_task(function *() {
+add_task(async function () {
   function createHandler(d) {
     var handler = new SMTP_RFC2821_handler(d);
     // Username needs to match the login information stored in the signons json
@@ -69,7 +69,7 @@ add_task(function *() {
   server = setupServerDaemon(createHandler);
 
   // Prepare files for passwords (generated by a script in bug 1018624).
-  yield setupForPassword("signons-mailnews1.8.json")
+  await setupForPassword("signons-mailnews1.8.json")
 
   registerAlertTestUtils();
 
diff --git a/mailnews/compose/test/unit/test_smtpPasswordFailure2.js b/mailnews/compose/test/unit/test_smtpPasswordFailure2.js
index 68b66cd488..b915b3f771 100644
--- a/mailnews/compose/test/unit/test_smtpPasswordFailure2.js
+++ b/mailnews/compose/test/unit/test_smtpPasswordFailure2.js
@@ -66,7 +66,7 @@ function promptPasswordPS(aParent, aDialogTitle, aText, aPassword, aCheckMsg,
   return false;
 }
 
-add_task(function *() {
+add_task(async function () {
   function createHandler(d) {
     var handler = new SMTP_RFC2821_handler(d);
     // Username needs to match the login information stored in the signons json
@@ -80,7 +80,7 @@ add_task(function *() {
   server = setupServerDaemon(createHandler);
 
   // Prepare files for passwords (generated by a script in bug 1018624).
-  yield setupForPassword("signons-mailnews1.8.json")
+  await setupForPassword("signons-mailnews1.8.json")
 
   registerAlertTestUtils();
 
diff --git a/mailnews/compose/test/unit/test_smtpPasswordFailure3.js b/mailnews/compose/test/unit/test_smtpPasswordFailure3.js
index 16b4dfa839..4cd11dafe3 100644
--- a/mailnews/compose/test/unit/test_smtpPasswordFailure3.js
+++ b/mailnews/compose/test/unit/test_smtpPasswordFailure3.js
@@ -64,7 +64,7 @@ function promptPasswordPS(aParent, aDialogTitle, aText, aPassword, aCheckMsg,
   return false;
 }
 
-add_task(function *() {
+add_task(async function () {
   function createHandler(d) {
     var handler = new SMTP_RFC2821_handler(d);
     handler.dropOnAuthFailure = true;
@@ -79,7 +79,7 @@ add_task(function *() {
   server = setupServerDaemon(createHandler);
 
   // Prepare files for passwords (generated by a script in bug 1018624).
-  yield setupForPassword("signons-mailnews1.8.json")
+  await setupForPassword("signons-mailnews1.8.json")
 
   registerAlertTestUtils();
 
diff --git a/mailnews/compose/test/unit/test_smtpProxy.js b/mailnews/compose/test/unit/test_smtpProxy.js
index 0ed774ed4a..ec6d600bfe 100644
--- a/mailnews/compose/test/unit/test_smtpProxy.js
+++ b/mailnews/compose/test/unit/test_smtpProxy.js
@@ -8,7 +8,7 @@ ChromeUtils.import("resource://testing-common/mailnews/PromiseTestUtils.jsm");
 const PORT = 25;
 var daemon, localserver, server;
 
-add_task(function* setup() {
+add_task(async function setup() {
   server = setupServerDaemon();
   daemon = server._daemon;
   server.start();
@@ -19,7 +19,7 @@ add_task(function* setup() {
 let CompFields = CC("@mozilla.org/messengercompose/composefields;1",
                     Ci.nsIMsgCompFields);
 
-add_task(function* sendMessage() {
+add_task(async function sendMessage() {
   equal(daemon.post, undefined);
   let identity = getSmtpIdentity("test@tinderbox.invalid", localserver);
   var testFile = do_get_file("data/message1.eml");
@@ -28,11 +28,11 @@ add_task(function* sendMessage() {
                                     "me@example.org",
                                     null, urlListener, null, null,
                                     false, {}, {});
-  yield urlListener.promise;
+  await urlListener.promise;
   notEqual(daemon.post, "");
 });
 
-add_task(function* cleanUp() {
+add_task(async function cleanUp() {
   NetworkTestUtils.shutdownServers();
 });
 
diff --git a/mailnews/imap/test/unit/test_filterNeedsBody.js b/mailnews/imap/test/unit/test_filterNeedsBody.js
index 517c523e96..53e059679d 100644
--- a/mailnews/imap/test/unit/test_filterNeedsBody.js
+++ b/mailnews/imap/test/unit/test_filterNeedsBody.js
@@ -53,7 +53,7 @@ function setup() {
 }
 
 // basic preparation done for each test
-function *runFilterAction() {
+async function runFilterAction() {
   let filterList = IMAPPump.incomingServer.getFilterList(null);
   while (filterList.filterCount)
     filterList.removeFilterAt(0);
@@ -68,7 +68,7 @@ function *runFilterAction() {
                               IMAPPump.mailbox.uidnext++, []));
   let listener = new PromiseTestUtils.PromiseUrlListener();
   IMAPPump.inbox.updateFolderWithListener(null, listener);
-  yield listener.promise;
+  await listener.promise;
 }
 
 function run_test() {
diff --git a/mailnews/imap/test/unit/test_imapFilterActions.js b/mailnews/imap/test/unit/test_imapFilterActions.js
index b55f41df54..5cb66db09b 100644
--- a/mailnews/imap/test/unit/test_imapFilterActions.js
+++ b/mailnews/imap/test/unit/test_imapFilterActions.js
@@ -59,118 +59,118 @@ var gTestArray =
   //},
   setupFilters,
   // The initial tests do not result in new messages added.
-  function *MoveToFolder() {
+  async function MoveToFolder() {
     gAction.type = Ci.nsMsgFilterAction.MoveToFolder;
     gAction.targetFolderUri = gSubfolder.URI;
     gInboxCount = folderCount(IMAPPump.inbox);
     gSubfolderCount = folderCount(gSubfolder);
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
 
     testCounts(false, 0, 0, 0);
     Assert.equal(gInboxCount, folderCount(IMAPPump.inbox));
     Assert.equal(gSubfolderCount + 1, folderCount(gSubfolder));
   },
   // do it again, sometimes that causes multiple downloads
-  function *MoveToFolder2() {
+  async function MoveToFolder2() {
     gAction.type = Ci.nsMsgFilterAction.MoveToFolder;
     gAction.targetFolderUri = gSubfolder.URI;
     gInboxCount = folderCount(IMAPPump.inbox);
     gSubfolderCount = folderCount(gSubfolder);
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
 
     testCounts(false, 0, 0, 0);
     Assert.equal(gInboxCount, folderCount(IMAPPump.inbox));
     Assert.equal(gSubfolderCount + 1, folderCount(gSubfolder));
   },
   /**/
-  function *MoveToFolderBody() {
+  async function MoveToFolderBody() {
     gAction.type = Ci.nsMsgFilterAction.MoveToFolder;
     gAction.targetFolderUri = gSubfolder.URI;
     gInboxCount = folderCount(IMAPPump.inbox);
     gSubfolderCount = folderCount(gSubfolder);
-    yield setupTest(gBodyFilter, gAction);
+    await setupTest(gBodyFilter, gAction);
 
     testCounts(false, 0, 0, 0);
     Assert.equal(gSubfolderCount + 1, folderCount(gSubfolder));
     // no net messages were added to the inbox
     Assert.equal(gInboxCount, folderCount(IMAPPump.inbox));
   },
-  function *MoveToFolderBody2() {
+  async function MoveToFolderBody2() {
     gAction.type = Ci.nsMsgFilterAction.MoveToFolder;
     gAction.targetFolderUri = gSubfolder.URI;
     gInboxCount = folderCount(IMAPPump.inbox);
     gSubfolderCount = folderCount(gSubfolder);
-    yield setupTest(gBodyFilter, gAction);
+    await setupTest(gBodyFilter, gAction);
 
     testCounts(false, 0, 0, 0);
     Assert.equal(gSubfolderCount + 1, folderCount(gSubfolder));
     // no net messages were added to the inbox
     Assert.equal(gInboxCount, folderCount(IMAPPump.inbox));
   },
-  function *MarkRead() {
+  async function MarkRead() {
     gAction.type = Ci.nsMsgFilterAction.MarkRead;
     gInboxCount = folderCount(IMAPPump.inbox);
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
     testCounts(false, 0, 0, 0);
     Assert.ok(gHeader.isRead);
     Assert.equal(gInboxCount + 1, folderCount(IMAPPump.inbox));
   },
-  function *MarkReadBody() {
+  async function MarkReadBody() {
     gAction.type = Ci.nsMsgFilterAction.MarkRead;
     gInboxCount = folderCount(IMAPPump.inbox);
-    yield setupTest(gBodyFilter, gAction);
+    await setupTest(gBodyFilter, gAction);
 
     testCounts(false, 0, 0, 0);
     Assert.ok(gHeader.isRead);
     Assert.equal(gInboxCount + 1, folderCount(IMAPPump.inbox));
   },
-  function *KillThread() {
+  async function KillThread() {
     gAction.type = Ci.nsMsgFilterAction.KillThread;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
 
     testCounts(false, 0, 0, 0);
     let thread = db().GetThreadContainingMsgHdr(gHeader);
     Assert.notEqual(0, thread.flags & Ci.nsMsgMessageFlags.Ignored);
   },
-  function *KillThreadBody() {
+  async function KillThreadBody() {
     gAction.type = Ci.nsMsgFilterAction.KillThread;
-    yield setupTest(gBodyFilter, gAction);
+    await setupTest(gBodyFilter, gAction);
 
     testCounts(false, 0, 0, 0);
     let thread = db().GetThreadContainingMsgHdr(gHeader);
     Assert.notEqual(0, thread.flags & Ci.nsMsgMessageFlags.Ignored);
   },
-  function *KillSubthread() {
+  async function KillSubthread() {
     gAction.type = Ci.nsMsgFilterAction.KillSubthread;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
 
     testCounts(false, 0, 0, 0);
     Assert.notEqual(0, gHeader.flags & Ci.nsMsgMessageFlags.Ignored);
   },
-  function *KillSubthreadBody() {
+  async function KillSubthreadBody() {
     gAction.type = Ci.nsMsgFilterAction.KillSubthread;
-    yield setupTest(gBodyFilter, gAction);
+    await setupTest(gBodyFilter, gAction);
 
     testCounts(false, 0, 0, 0);
     Assert.notEqual(0, gHeader.flags & Ci.nsMsgMessageFlags.Ignored);
   },
-  function *DoNothing() {
+  async function DoNothing() {
     gAction.type = Ci.nsMsgFilterAction.StopExecution;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
 
     testCounts(true, 1, 1, 1);
   },
-  function *DoNothingBody() {
+  async function DoNothingBody() {
     gAction.type = Ci.nsMsgFilterAction.StopExecution;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
 
     testCounts(true, 1, 1, 1);
   },
   // this tests for marking message as junk
-  function *JunkScore() {
+  async function JunkScore() {
     gAction.type = Ci.nsMsgFilterAction.JunkScore;
     gAction.junkScore = 100;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
 
     // marking as junk resets new but not unread
     testCounts(false, 1, 0, 0);
@@ -178,10 +178,10 @@ var gTestArray =
     Assert.equal(gHeader.getStringProperty("junkscoreorigin"), "filter");
   },
   // this tests for marking message as junk
-  function *JunkScoreBody() {
+  async function JunkScoreBody() {
     gAction.type = Ci.nsMsgFilterAction.JunkScore;
     gAction.junkScore = 100;
-    yield setupTest(gBodyFilter, gAction);
+    await setupTest(gBodyFilter, gAction);
 
     // marking as junk resets new but not unread
     testCounts(false, 1, 0, 0);
@@ -189,135 +189,135 @@ var gTestArray =
     Assert.equal(gHeader.getStringProperty("junkscoreorigin"), "filter");
   },
   // The remaining tests add new messages
-  function *MarkUnread() {
+  async function MarkUnread() {
     gAction.type = Ci.nsMsgFilterAction.MarkUnread;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
 
     testCounts(true, 1, 1, 1);
     Assert.ok(!gHeader.isRead);
   },
-  function *MarkUnreadBody() {
+  async function MarkUnreadBody() {
     gAction.type = Ci.nsMsgFilterAction.MarkUnread;
-    yield setupTest(gBodyFilter, gAction);
+    await setupTest(gBodyFilter, gAction);
 
     testCounts(true, 1, 1, 1);
     Assert.ok(!gHeader.isRead);
   },
-  function *WatchThread() {
+  async function WatchThread() {
     gAction.type = Ci.nsMsgFilterAction.WatchThread;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
 
     testCounts(true, 1, 1, 1);
     let thread = db().GetThreadContainingMsgHdr(gHeader);
     Assert.notEqual(0, thread.flags & Ci.nsMsgMessageFlags.Watched);
   },
-  function *WatchThreadBody() {
+  async function WatchThreadBody() {
     gAction.type = Ci.nsMsgFilterAction.WatchThread;
-    yield setupTest(gBodyFilter, gAction);
+    await setupTest(gBodyFilter, gAction);
 
     testCounts(true, 1, 1, 1);
     let thread = db().GetThreadContainingMsgHdr(gHeader);
     Assert.notEqual(0, thread.flags & Ci.nsMsgMessageFlags.Watched);
   },
-  function *MarkFlagged() {
+  async function MarkFlagged() {
     gAction.type = Ci.nsMsgFilterAction.MarkFlagged;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
 
     testCounts(true, 1, 1, 1);
     Assert.ok(gHeader.isFlagged);
   },
-  function *MarkFlaggedBody() {
+  async function MarkFlaggedBody() {
     gAction.type = Ci.nsMsgFilterAction.MarkFlagged;
-    yield setupTest(gBodyFilter, gAction);
+    await setupTest(gBodyFilter, gAction);
 
     testCounts(true, 1, 1, 1);
     Assert.ok(gHeader.isFlagged);
   },
-  function *ChangePriority() {
+  async function ChangePriority() {
     gAction.type = Ci.nsMsgFilterAction.ChangePriority;
     gAction.priority = Ci.nsMsgPriority.highest;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
 
     testCounts(true, 1, 1, 1);
     Assert.equal(Ci.nsMsgPriority.highest, gHeader.priority);
   },
-  function *ChangePriorityBody() {
+  async function ChangePriorityBody() {
     gAction.type = Ci.nsMsgFilterAction.ChangePriority;
     gAction.priority = Ci.nsMsgPriority.highest;
-    yield setupTest(gBodyFilter, gAction);
+    await setupTest(gBodyFilter, gAction);
 
     testCounts(true, 1, 1, 1);
     Assert.equal(Ci.nsMsgPriority.highest, gHeader.priority);
   },
-  function *Label() {
+  async function Label() {
     gAction.type = Ci.nsMsgFilterAction.Label;
     gAction.label = 2;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
 
     testCounts(true, 1, 1, 1);
     Assert.equal(2, gHeader.label);
   },
-  function *LabelBody() {
+  async function LabelBody() {
     gAction.type = Ci.nsMsgFilterAction.Label;
     gAction.label = 3;
-    yield setupTest(gBodyFilter, gAction);
+    await setupTest(gBodyFilter, gAction);
 
     testCounts(true, 1, 1, 1);
     Assert.equal(3, gHeader.label);
   },
-  function *AddTag() {
+  async function AddTag() {
     gAction.type = Ci.nsMsgFilterAction.AddTag;
     gAction.strValue = "TheTag";
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
 
     testCounts(true, 1, 1, 1);
     Assert.equal(gHeader.getStringProperty("keywords"), "thetag");
   },
-  function *AddTagBody() {
+  async function AddTagBody() {
     gAction.type = Ci.nsMsgFilterAction.AddTag;
     gAction.strValue = "TheTag2";
-    yield setupTest(gBodyFilter, gAction);
+    await setupTest(gBodyFilter, gAction);
 
     testCounts(true, 1, 1, 1);
     Assert.equal(gHeader.getStringProperty("keywords"), "thetag2");
   },
   // this tests for marking message as good
-  function *JunkScoreAsGood() {
+  async function JunkScoreAsGood() {
     gAction.type = Ci.nsMsgFilterAction.JunkScore;
     gAction.junkScore = 0;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
 
     testCounts(true, 1, 1, 1);
     Assert.equal(gHeader.getStringProperty("junkscore"), "0");
     Assert.equal(gHeader.getStringProperty("junkscoreorigin"), "filter");
   },
   // this tests for marking message as good
-  function *JunkScoreAsGoodBody() {
+  async function JunkScoreAsGoodBody() {
     gAction.type = Ci.nsMsgFilterAction.JunkScore;
     gAction.junkScore = 0;
-    yield setupTest(gBodyFilter, gAction);
+    await setupTest(gBodyFilter, gAction);
 
     testCounts(true, 1, 1, 1);
     Assert.equal(gHeader.getStringProperty("junkscore"), "0");
     Assert.equal(gHeader.getStringProperty("junkscoreorigin"), "filter");
   },
-  function *CopyToFolder() {
+  async function CopyToFolder() {
     gAction.type = Ci.nsMsgFilterAction.CopyToFolder;
     gAction.targetFolderUri = gSubfolder.URI;
     gInboxCount = folderCount(IMAPPump.inbox);
     gSubfolderCount = folderCount(gSubfolder);
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
 
     testCounts(true, 1, 1, 1);
     Assert.equal(gInboxCount + 1, folderCount(IMAPPump.inbox));
     Assert.equal(gSubfolderCount + 1, folderCount(gSubfolder));
   },
-  function *CopyToFolderBody() {
+  async function CopyToFolderBody() {
     gAction.type = Ci.nsMsgFilterAction.CopyToFolder;
     gAction.targetFolderUri = gSubfolder.URI;
     gInboxCount = folderCount(IMAPPump.inbox);
     gSubfolderCount = folderCount(gSubfolder);
-    yield setupTest(gBodyFilter, gAction);
+    await setupTest(gBodyFilter, gAction);
 
     testCounts(true, 1, 1, 1);
     Assert.equal(gInboxCount + 1, folderCount(IMAPPump.inbox));
@@ -388,7 +388,7 @@ function setupFilters()
 // basic preparation done for each test
 function setupTest(aFilter, aAction)
 {
-  return Task.spawn(function* () {
+  return Task.spawn(async function () {
     let filterList = IMAPPump.incomingServer.getFilterList(null);
     while (filterList.filterCount)
       filterList.removeFilterAt(0);
@@ -412,8 +412,8 @@ function setupTest(aFilter, aAction)
                             IMAPPump.mailbox.uidnext++, []));
     let promiseUrlListener = new PromiseTestUtils.PromiseUrlListener();
     IMAPPump.inbox.updateFolderWithListener(null, promiseUrlListener);
-    yield promiseUrlListener.promise;
-    yield PromiseTestUtils.promiseDelay(200);
+    await promiseUrlListener.promise;
+    await PromiseTestUtils.promiseDelay(200);
   });
 }
 
diff --git a/mailnews/imap/test/unit/test_imapFilterActionsPostplugin.js b/mailnews/imap/test/unit/test_imapFilterActionsPostplugin.js
index cf829ea0b8..26823696d1 100644
--- a/mailnews/imap/test/unit/test_imapFilterActionsPostplugin.js
+++ b/mailnews/imap/test/unit/test_imapFilterActionsPostplugin.js
@@ -48,129 +48,129 @@ var gTestArray =
 [
   setupIMAPPump,
   setupFilters,
-  function *DoNothing() {
+  async function DoNothing() {
     gAction.type = Ci.nsMsgFilterAction.StopExecution;
     gInboxCount = folderCount(IMAPPump.inbox);
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
     testCounts(false, 1, 0, 0);
     Assert.equal(gInboxCount + 1, folderCount(IMAPPump.inbox));
   },
-  function *Delete() {
+  async function Delete() {
     gAction.type = Ci.nsMsgFilterAction.Delete;
     gInboxCount = folderCount(IMAPPump.inbox);
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
     testCounts(false, 0, 0, 0);
     Assert.equal(gInboxCount, folderCount(IMAPPump.inbox));
   },
-  function *MoveToFolder() {
+  async function MoveToFolder() {
     gAction.type = Ci.nsMsgFilterAction.MoveToFolder;
     gAction.targetFolderUri = gSubfolder.URI;
     gInboxCount = folderCount(IMAPPump.inbox);
     gSubfolderCount = folderCount(gSubfolder);
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
 
     testCounts(false, 0, 0, 0);
     Assert.equal(gSubfolderCount + 1, folderCount(gSubfolder));
   // no net messages were added to the inbox
     Assert.equal(gInboxCount, folderCount(IMAPPump.inbox));
   },
-  function *MarkRead() {
+  async function MarkRead() {
     gAction.type = Ci.nsMsgFilterAction.MarkRead;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
     testCounts(false, 0, 0, 0);
     Assert.ok(gHeader.isRead);
   },
-  function *KillThread() {
+  async function KillThread() {
     gAction.type = Ci.nsMsgFilterAction.KillThread;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
     // In non-postplugin, count here is 0 and not 1.  Need to investigate.
     testCounts(false, 1, 0, 0);
     let thread = db().GetThreadContainingMsgHdr(gHeader);
     Assert.notEqual(0, thread.flags & Ci.nsMsgMessageFlags.Ignored);
   },
-  function *WatchThread() {
+  async function WatchThread() {
     gAction.type = Ci.nsMsgFilterAction.WatchThread;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
     // In non-postplugin, count here is 0 and not 1.  Need to investigate.
     testCounts(false, 1, 0, 0);
     let thread = db().GetThreadContainingMsgHdr(gHeader);
     Assert.notEqual(0, thread.flags & Ci.nsMsgMessageFlags.Watched);
   },
-  function *KillSubthread() {
+  async function KillSubthread() {
     gAction.type = Ci.nsMsgFilterAction.KillSubthread;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
     // In non-postplugin, count here is 0 and not 1.  Need to investigate.
     testCounts(false, 1, 0, 0);
     Assert.notEqual(0, gHeader.flags & Ci.nsMsgMessageFlags.Ignored);
   },
   // this tests for marking message as junk
-  function *JunkScore() {
+  async function JunkScore() {
     gAction.type = Ci.nsMsgFilterAction.JunkScore;
     gAction.junkScore = 100;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
     // marking as junk resets new but not unread
     testCounts(false, 1, 0, 0);
     Assert.equal(gHeader.getStringProperty("junkscore"), "100");
     Assert.equal(gHeader.getStringProperty("junkscoreorigin"), "filter");
   },
-  function *MarkUnread() {
+  async function MarkUnread() {
     gAction.type = Ci.nsMsgFilterAction.MarkUnread;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
     testCounts(true, 1, 1, 1);
     Assert.ok(!gHeader.isRead);
   },
-  function *MarkFlagged() {
+  async function MarkFlagged() {
     gAction.type = Ci.nsMsgFilterAction.MarkFlagged;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
     testCounts(true, 1, 1, 1);
     Assert.ok(gHeader.isFlagged);
   },
-  function *ChangePriority() {
+  async function ChangePriority() {
     gAction.type = Ci.nsMsgFilterAction.ChangePriority;
     gAction.priority = Ci.nsMsgPriority.highest;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
     testCounts(true, 1, 1, 1);
     Assert.equal(Ci.nsMsgPriority.highest, gHeader.priority);
   },
-  function *Label() {
+  async function Label() {
     gAction.type = Ci.nsMsgFilterAction.Label;
     gAction.label = 2;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
     testCounts(true, 1, 1, 1);
     Assert.equal(2, gHeader.label);
   },
-  function *AddTag() {
+  async function AddTag() {
     gAction.type = Ci.nsMsgFilterAction.AddTag;
     gAction.strValue = "TheTag";
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
     testCounts(true, 1, 1, 1);
     Assert.equal(gHeader.getStringProperty("keywords"), "thetag");
   },
   // this tests for marking message as good
-  function *JunkScoreAsGood() {
+  async function JunkScoreAsGood() {
     gAction.type = Ci.nsMsgFilterAction.JunkScore;
     gAction.junkScore = 0;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
     testCounts(true, 1, 1, 1);
     Assert.equal(gHeader.getStringProperty("junkscore"), "0");
     Assert.equal(gHeader.getStringProperty("junkscoreorigin"), "filter");
   },
-  function *CopyToFolder() {
+  async function CopyToFolder() {
     gAction.type = Ci.nsMsgFilterAction.CopyToFolder;
     gAction.targetFolderUri = gSubfolder.URI;
     gInboxCount = folderCount(IMAPPump.inbox);
     gSubfolderCount = folderCount(gSubfolder);
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
     testCounts(true, 1, 1, 1);
     Assert.equal(gInboxCount + 1, folderCount(IMAPPump.inbox));
     Assert.equal(gSubfolderCount + 1, folderCount(gSubfolder));
   },
-  function *Custom() {
+  async function Custom() {
     gAction.type = Ci.nsMsgFilterAction.Custom;
     gAction.customId = 'mailnews@mozilla.org#testOffline';
     gAction.strValue = 'true';
     actionTestOffline.needsBody = true;
-    yield setupTest(gFilter, gAction);
+    await setupTest(gFilter, gAction);
     testCounts(true, 1, 1, 1);
   },
   /**/
@@ -217,7 +217,7 @@ function setupFilters()
 // basic preparation done for each test
 function setupTest(aFilter, aAction)
 {
-  return Task.spawn(function* () {
+  return Task.spawn(async function () {
     let filterList = IMAPPump.incomingServer.getFilterList(null);
     while (filterList.filterCount)
       filterList.removeFilterAt(0);
@@ -239,8 +239,8 @@ function setupTest(aFilter, aAction)
                             IMAPPump.mailbox.uidnext++, []));
     let promiseUrlListener = new PromiseTestUtils.PromiseUrlListener();
     IMAPPump.inbox.updateFolderWithListener(null, promiseUrlListener);
-    yield promiseUrlListener.promise;
-    yield PromiseTestUtils.promiseDelay(200);
+    await promiseUrlListener.promise;
+    await PromiseTestUtils.promiseDelay(200);
   });
 }
 
diff --git a/mailnews/imap/test/unit/test_imapMove.js b/mailnews/imap/test/unit/test_imapMove.js
index d69c8921ab..06a32540d5 100644
--- a/mailnews/imap/test/unit/test_imapMove.js
+++ b/mailnews/imap/test/unit/test_imapMove.js
@@ -25,23 +25,23 @@ function setupCUSTOM1() {
   Services.prefs.setBoolPref("mail.server.default.autosync_offline_stores", false);
 }
 
-function *startTest()
+async function startTest()
 {
   IMAPPump.incomingServer.rootFolder.createSubfolder("folder 1", null);
-  yield PromiseTestUtils.promiseFolderAdded("folder 1");
+  await PromiseTestUtils.promiseFolderAdded("folder 1");
 
   addImapMessage();
   let listener = new PromiseTestUtils.PromiseUrlListener();
   IMAPPump.inbox.updateFolderWithListener(null, listener);
-  yield listener.promise;
+  await listener.promise;
 
   // ...and download for offline use.
   let promiseUrlListener = new PromiseTestUtils.PromiseUrlListener();
   IMAPPump.inbox.downloadAllForOffline(promiseUrlListener, null);
-  yield promiseUrlListener.promise;
+  await promiseUrlListener.promise;
 }
 
-function *doMove() {
+async function doMove() {
   var messages = Cc["@mozilla.org/array;1"].createInstance(Ci.nsIMutableArray);
   let rootFolder = IMAPPump.incomingServer.rootFolder;
   gFolder1 = rootFolder.getChildNamed("folder 1")
@@ -53,14 +53,14 @@ function *doMove() {
   MailServices.copy.CopyMessages(IMAPPump.inbox, messages, gFolder1, true,
                                  listener, null, false);
   IMAPPump.server.performTest("UID MOVE");
-  yield listener.promise;
+  await listener.promise;
 }
 
-function *testMove() {
+async function testMove() {
   Assert.equal(IMAPPump.inbox.getTotalMessages(false), 0);
   let listener = new PromiseTestUtils.PromiseUrlListener();
   gFolder1.updateFolderWithListener(null, listener);
-  yield listener.promise;
+  await listener.promise;
   Assert.equal(gFolder1.getTotalMessages(false), 1);
 
   // maildir should also delete the files.
diff --git a/mailnews/imap/test/unit/test_imapPasswordFailure.js b/mailnews/imap/test/unit/test_imapPasswordFailure.js
index 47e25fe846..f69c18341e 100644
--- a/mailnews/imap/test/unit/test_imapPasswordFailure.js
+++ b/mailnews/imap/test/unit/test_imapPasswordFailure.js
@@ -57,11 +57,11 @@ function promptPasswordPS(aParent, aDialogTitle, aText, aPassword, aCheckMsg,
   return false;
 }
 
-add_task(function *() {
+add_task(async function () {
   do_test_pending();
 
   // Prepare files for passwords (generated by a script in bug 1018624).
-  yield setupForPassword("signons-mailnews1.8-imap.json")
+  await setupForPassword("signons-mailnews1.8-imap.json")
 
   registerAlertTestUtils();
 
diff --git a/mailnews/imap/test/unit/test_imapProxy.js b/mailnews/imap/test/unit/test_imapProxy.js
index 0cd1c5ccc3..4d6781db6d 100644
--- a/mailnews/imap/test/unit/test_imapProxy.js
+++ b/mailnews/imap/test/unit/test_imapProxy.js
@@ -10,7 +10,7 @@ var server, daemon, incomingServer;
 
 const PORT = 143;
 
-add_task(function* setup() {
+add_task(async function setup() {
   // Disable new mail notifications
   Services.prefs.setBoolPref("mail.biff.play_sound", false);
   Services.prefs.setBoolPref("mail.biff.show_alert", false);
@@ -40,7 +40,7 @@ add_task(function* setup() {
   imapAccount.incomingServer = incomingServer;
 });
 
-add_task(function* downloadEmail() {
+add_task(async function downloadEmail() {
   let inboxFolder = incomingServer.rootFolder.getChildNamed("INBOX");
 
   // Check that we haven't got any messages in the folder, if we have its a test
@@ -50,13 +50,13 @@ add_task(function* downloadEmail() {
   // Now get the mail
   let asyncUrlListener = new PromiseTestUtils.PromiseUrlListener();
   inboxFolder.getNewMessages(null, asyncUrlListener);
-  yield asyncUrlListener.promise;
+  await asyncUrlListener.promise;
 
   // We downloaded a message, so it works!
   Assert.equal(inboxFolder.getTotalMessages(false), 1);
 });
 
-add_task(function* cleanUp() {
+add_task(async function cleanUp() {
   NetworkTestUtils.shutdownServers();
   incomingServer.closeCachedConnections();
   server.stop();
diff --git a/mailnews/local/test/unit/test_duplicateKey.js b/mailnews/local/test/unit/test_duplicateKey.js
index 88ad994d0c..cf803ba846 100644
--- a/mailnews/local/test/unit/test_duplicateKey.js
+++ b/mailnews/local/test/unit/test_duplicateKey.js
@@ -9,14 +9,14 @@
 load("../../../resources/POP3pump.js");
 ChromeUtils.import("resource://testing-common/mailnews/PromiseTestUtils.jsm");
 
-add_task(function* runPump() {
+add_task(async function runPump() {
 
   gPOP3Pump.files = ["../../../data/bugmail1",
                      "../../../data/bugmail1",
                      "../../../data/bugmail1",
                      "../../../data/bugmail1",
                      "../../../data/bugmail1"];
-  yield gPOP3Pump.run();
+  await gPOP3Pump.run();
 
   // get message headers for the inbox folder
   var hdrs = showMessages(localAccountUtils.inboxFolder);
@@ -44,7 +44,7 @@ add_task(function* runPump() {
   // compact
   var listener = new PromiseTestUtils.PromiseUrlListener();
   localAccountUtils.inboxFolder.compact(listener, null);
-  yield listener.promise;
+  await listener.promise;
 
   dump("Messages after compact\n");
   hdrs = showMessages(localAccountUtils.inboxFolder);
@@ -53,7 +53,7 @@ add_task(function* runPump() {
   // Add some more messages. This fails in nsMsgDatabase::AddNewHdrToDB with
   // NS_ERROR("adding hdr that already exists") before bug 1202105.
   gPOP3Pump.files = ["../../../data/draft1"];
-  yield gPOP3Pump.run();
+  await gPOP3Pump.run();
 
   dump("Messages after new message\n");
   hdrs = showMessages(localAccountUtils.inboxFolder);
diff --git a/mailnews/local/test/unit/test_movemailDownload.js b/mailnews/local/test/unit/test_movemailDownload.js
index 0f9c951c42..63adaf82ce 100644
--- a/mailnews/local/test/unit/test_movemailDownload.js
+++ b/mailnews/local/test/unit/test_movemailDownload.js
@@ -63,9 +63,9 @@ var gTestArray = [
     }
     Assert.equal(msgCount, 3);
   },
-  function *streamMessages() {
+  async function streamMessages() {
     for (let msgHdr of gMsgHdrs)
-      yield streamNextMessage(msgHdr);
+      await streamNextMessage(msgHdr);
   }
 ];
 
@@ -81,7 +81,7 @@ function run_test()
   run_next_test();
 }
 
-var streamNextMessage = Task.async(function* (aMsgHdr) {
+var streamNextMessage = async function (aMsgHdr) {
   let messenger = Cc["@mozilla.org/messenger;1"].createInstance(Ci.nsIMessenger);
   let msgURI = aMsgHdr.folder.getUriForMsg(aMsgHdr);
   dump("streaming msg " + msgURI + " store token = " +
@@ -89,6 +89,6 @@ var streamNextMessage = Task.async(function* (aMsgHdr) {
   let msgServ = messenger.messageServiceFromURI(msgURI);
   let streamListener = new PromiseTestUtils.PromiseStreamListener();
   msgServ.streamMessage(msgURI, streamListener, null, null, false, "", true);
-  let data = yield streamListener.promise;
+  let data = await streamListener.promise;
   Assert.ok(data.startsWith("From "));
-});
+};
diff --git a/mailnews/local/test/unit/test_pop3MultiCopy.js b/mailnews/local/test/unit/test_pop3MultiCopy.js
index 1d5d434b80..7945c82a03 100644
--- a/mailnews/local/test/unit/test_pop3MultiCopy.js
+++ b/mailnews/local/test/unit/test_pop3MultiCopy.js
@@ -14,7 +14,7 @@ var testSubjects = ["[Bug 397009] A filter will let me tag, but not untag",
 Services.prefs.setCharPref("mail.serverDefaultStoreContractID",
                            "@mozilla.org/msgstore/maildirstore;1");
 
-add_task(function* runPump() {
+add_task(async function runPump() {
   // Test for multiple message copy for maildir.
   let storeID = "@mozilla.org/msgstore/maildirstore;1";
   gPOP3Pump.resetPluggableStore(storeID);
@@ -26,7 +26,7 @@ add_task(function* runPump() {
 
   gPOP3Pump.files = ["../../../data/bugmail1",
                      "../../../data/draft1"];
-  yield gPOP3Pump.run();
+  await gPOP3Pump.run();
 
   // get message headers for the inbox folder
   let inbox = gPOP3Pump.fakeServer
@@ -56,7 +56,7 @@ add_task(function* runPump() {
   let promiseCopyListener = new PromiseTestUtils.PromiseCopyListener();
   MailServices.copy.CopyMessages(inbox, messages, testFolder, false,
                                  promiseCopyListener, null, false);
-  yield promiseCopyListener.promise;
+  await promiseCopyListener.promise;
 
   // Check the destination headers.
   messages.clear();
diff --git a/mailnews/local/test/unit/test_pop3MultiCopy2.js b/mailnews/local/test/unit/test_pop3MultiCopy2.js
index 286cb7de54..9056de60d9 100644
--- a/mailnews/local/test/unit/test_pop3MultiCopy2.js
+++ b/mailnews/local/test/unit/test_pop3MultiCopy2.js
@@ -19,7 +19,7 @@ gPOP3Pump.files = ["../../../data/bugmail1",
 var gTestSubjects = ["[Bug 397009] A filter will let me tag, but not untag",
                      "Hello, did you receive my bugmail?"];
 
-add_task(function* setupFolders() {
+add_task(async function setupFolders() {
   let storeID = "@mozilla.org/msgstore/maildirstore;1";
   resetPluggableStoreLocal(storeID);
 
@@ -31,10 +31,10 @@ add_task(function* setupFolders() {
                                  .QueryInterface(Ci.nsIMsgLocalMailFolder)
                                  .createLocalSubfolder("test");
   dump("testFolder is at " + gTestFolder.filePath.path + "\n");
-  yield gPOP3Pump.run();
+  await gPOP3Pump.run();
 });
 
-add_task(function* maildirToMbox() {
+add_task(async function maildirToMbox() {
   // Test for multiple message copy for maildir->mbox.
 
   // get message headers for the inbox folder
@@ -56,7 +56,7 @@ add_task(function* maildirToMbox() {
   let promiseCopyListener = new PromiseTestUtils.PromiseCopyListener();
   MailServices.copy.CopyMessages(gInboxFolder, messages, gTestFolder, true,
                                  promiseCopyListener, null, false);
-  yield promiseCopyListener.promise;
+  await promiseCopyListener.promise;
 
   // Check the destination headers.
   messages.clear();
@@ -88,7 +88,7 @@ add_task(function* maildirToMbox() {
   }
 });
 
-add_task(function* mboxToMaildir() {
+add_task(async function mboxToMaildir() {
   // Test for multiple message copy for mbox->maildir.
 
   // Accumulate messages to copy.
@@ -104,7 +104,7 @@ add_task(function* mboxToMaildir() {
   let promiseCopyListener = new PromiseTestUtils.PromiseCopyListener();
   MailServices.copy.CopyMessages(gTestFolder, messages, gInboxFolder, true,
                                  promiseCopyListener, null, false);
-  yield promiseCopyListener.promise;
+  await promiseCopyListener.promise;
 
   // Check the destination headers.
   messages.clear();
diff --git a/mailnews/local/test/unit/test_pop3Password.js b/mailnews/local/test/unit/test_pop3Password.js
index 4603671f6d..a1d408d120 100644
--- a/mailnews/local/test/unit/test_pop3Password.js
+++ b/mailnews/local/test/unit/test_pop3Password.js
@@ -105,7 +105,7 @@ function testNext() {
   }
 }
 
-add_task(function *() {
+add_task(async function () {
   // Disable new mail notifications
   Services.prefs.setBoolPref("mail.biff.play_sound", false);
   Services.prefs.setBoolPref("mail.biff.show_alert", false);
@@ -113,7 +113,7 @@ add_task(function *() {
   Services.prefs.setBoolPref("mail.biff.animate_dock_icon", false);
 
   // Prepare files for passwords (generated by a script in bug 1018624).
-  yield setupForPassword("signons-mailnews1.8.json");
+  await setupForPassword("signons-mailnews1.8.json");
 
   // Set up the Server
   var serverArray = setupServerDaemon();
diff --git a/mailnews/local/test/unit/test_pop3Password2.js b/mailnews/local/test/unit/test_pop3Password2.js
index 28167257de..f1653fcdaf 100644
--- a/mailnews/local/test/unit/test_pop3Password2.js
+++ b/mailnews/local/test/unit/test_pop3Password2.js
@@ -107,7 +107,7 @@ function testNext() {
   }
 }
 
-add_task(function *() {
+add_task(async function () {
   // Disable new mail notifications
   Services.prefs.setBoolPref("mail.biff.play_sound", false);
   Services.prefs.setBoolPref("mail.biff.show_alert", false);
@@ -141,7 +141,7 @@ add_task(function *() {
   Services.prefs.setCharPref("mail.server.server2.userName", "othername");
 
   // Prepare files for passwords (generated by a script in bug 1018624).
-  yield setupForPassword("signons-mailnews1.8-alt.json");
+  await setupForPassword("signons-mailnews1.8-alt.json");
 
   // Set up the Server
   var serverArray = setupServerDaemon();
diff --git a/mailnews/local/test/unit/test_pop3Password3.js b/mailnews/local/test/unit/test_pop3Password3.js
index 6fbce77b35..d88e1b01ea 100644
--- a/mailnews/local/test/unit/test_pop3Password3.js
+++ b/mailnews/local/test/unit/test_pop3Password3.js
@@ -14,9 +14,9 @@ var kProtocol = "pop3";
 var kHostname = "localhost";
 var kServerUrl = "mailbox://" + kHostname;
 
-add_task(function *() {
+add_task(async function () {
   // Prepare files for passwords (generated by a script in bug 1018624).
-  yield setupForPassword("signons-mailnews1.8-multiple.json");
+  await setupForPassword("signons-mailnews1.8-multiple.json");
 
   // Set up the basic accounts and folders.
   // We would use createPop3ServerAndLocalFolders() however we want to have
diff --git a/mailnews/local/test/unit/test_pop3PasswordFailure.js b/mailnews/local/test/unit/test_pop3PasswordFailure.js
index 3ffd0baac5..0b3e55d2ec 100644
--- a/mailnews/local/test/unit/test_pop3PasswordFailure.js
+++ b/mailnews/local/test/unit/test_pop3PasswordFailure.js
@@ -174,7 +174,7 @@ function* end_test()
   do_test_finished();
 }
 
-add_task(function *() {
+add_task(async function () {
   // Disable new mail notifications
   Services.prefs.setBoolPref("mail.biff.play_sound", false);
   Services.prefs.setBoolPref("mail.biff.show_alert", false);
@@ -183,7 +183,7 @@ add_task(function *() {
   Services.prefs.setBoolPref("signon.debug", true);
 
   // Prepare files for passwords (generated by a script in bug 1018624).
-  yield setupForPassword("signons-mailnews1.8.json");
+  await setupForPassword("signons-mailnews1.8.json");
 
   registerAlertTestUtils();
 
diff --git a/mailnews/local/test/unit/test_pop3Proxy.js b/mailnews/local/test/unit/test_pop3Proxy.js
index eb30f69b20..c3c78e0c28 100644
--- a/mailnews/local/test/unit/test_pop3Proxy.js
+++ b/mailnews/local/test/unit/test_pop3Proxy.js
@@ -9,7 +9,7 @@ const PORT = 110;
 
 var server, daemon, incomingServer;
 
-add_task(function* setup() {
+add_task(async function setup() {
   // Disable new mail notifications
   Services.prefs.setBoolPref("mail.biff.play_sound", false);
   Services.prefs.setBoolPref("mail.biff.show_alert", false);
@@ -27,7 +27,7 @@ add_task(function* setup() {
   daemon.setMessages(["message1.eml"]);
 });
 
-add_task(function* downloadEmail() {
+add_task(async function downloadEmail() {
   // Check that we haven't got any messages in the folder, if we have its a test
   // setup issue.
   equal(localAccountUtils.inboxFolder.getTotalMessages(false), 0);
@@ -36,13 +36,13 @@ add_task(function* downloadEmail() {
   let urlListener = new PromiseTestUtils.PromiseUrlListener();
   MailServices.pop3.GetNewMail(null, urlListener, localAccountUtils.inboxFolder,
                                incomingServer);
-  yield urlListener.promise;
+  await urlListener.promise;
 
   // We downloaded a message, so it works!
   equal(localAccountUtils.inboxFolder.getTotalMessages(false), 1);
 });
 
-add_task(function* cleanUp() {
+add_task(async function cleanUp() {
   NetworkTestUtils.shutdownServers();
   incomingServer.closeCachedConnections();
   server.stop();
diff --git a/mailnews/local/test/unit/test_pop3Pump.js b/mailnews/local/test/unit/test_pop3Pump.js
index 1afe530737..d493dc175b 100644
--- a/mailnews/local/test/unit/test_pop3Pump.js
+++ b/mailnews/local/test/unit/test_pop3Pump.js
@@ -7,7 +7,7 @@ load("../../../resources/POP3pump.js");
 var testSubjects = ["[Bug 397009] A filter will let me tag, but not untag",
                     "Hello, did you receive my bugmail?"];
 
-add_task(function* runPump() {
+add_task(async function runPump() {
   // demonstration of access to the local inbox folder
   dump("local inbox folder " + localAccountUtils.inboxFolder.URI + " is loaded\n");
   // demonstration of access to the fake server
@@ -15,7 +15,7 @@ add_task(function* runPump() {
 
   gPOP3Pump.files = ["../../../data/bugmail1",
                       "../../../data/draft1"];
-  yield gPOP3Pump.run();
+  await gPOP3Pump.run();
 
   // get message headers for the inbox folder
   let enumerator = localAccountUtils.inboxFolder.msgDatabase.EnumerateMessages();
diff --git a/mailnews/mime/test/unit/test_structured_headers.js b/mailnews/mime/test/unit/test_structured_headers.js
index 22f156f010..bea2ac23e7 100644
--- a/mailnews/mime/test/unit/test_structured_headers.js
+++ b/mailnews/mime/test/unit/test_structured_headers.js
@@ -21,7 +21,7 @@ function verifyError(block, errorCode) {
 var StructuredHeaders = CC("@mozilla.org/messenger/structuredheaders;1",
                            Ci.msgIWritableStructuredHeaders);
 
-add_task(function* check_addressing() {
+add_task(async function check_addressing() {
   let headers = new StructuredHeaders();
   headers.setHeader("To", [{name: "undisclosed-recipients", group: []}]);
   Assert.ok(Array.isArray(headers.getHeader("To")));
@@ -44,7 +44,7 @@ add_task(function* check_addressing() {
     "\"Comma, Name\" <test@foo.invalid>");
 });
 
-add_task(function* check_custom_header() {
+add_task(async function check_custom_header() {
   // Load an extension for our custom header.
   let url = Services.io.newFileURI(do_get_file("custom_header.js")).spec;
   let promise = new Promise((resolve, reject) => {
@@ -60,7 +60,7 @@ add_task(function* check_custom_header() {
     .getService(Ci.nsICategoryManager)
     .addCategoryEntry("custom-mime-encoder", "X-Unusual", url, false, true);
   // The category manager doesn't fire until a later timestep.
-  yield promise;
+  await promise;
   let headers = new StructuredHeaders();
   headers.setRawHeader("X-Unusual", "10", null);
   Assert.equal(headers.getHeader("X-Unusual"), 16);
@@ -68,7 +68,7 @@ add_task(function* check_custom_header() {
   Assert.equal(headers.getRawHeader("X-Unusual"), "20");
 });
 
-add_task(function* check_raw() {
+add_task(async function check_raw() {
   let headers = new StructuredHeaders();
   Assert.ok(!headers.hasHeader("Date"));
   let day = new Date("2000-01-01T00:00:00Z");
@@ -139,7 +139,7 @@ add_task(function* check_raw() {
   Assert.ok(moreHeaders.hasHeader("Date"));
 })
 
-add_task(function* check_nsIMimeHeaders() {
+add_task(async function check_nsIMimeHeaders() {
   let headers = Cc["@mozilla.org/messenger/mimeheaders;1"]
                   .createInstance(Ci.nsIMimeHeaders);
   Assert.ok(headers instanceof Ci.msgIStructuredHeaders);
@@ -162,7 +162,7 @@ add_task(function* check_nsIMimeHeaders() {
   }
 });
 
-add_task(function* checkBuildMimeText() {
+add_task(async function checkBuildMimeText() {
   let headers = new StructuredHeaders();
   headers.setHeader("To", [{name: "François Smith", email: "user@☃.invalid"}]);
   headers.setHeader("From", [{name: "John Doe", email: "jdoe@test.invalid"}]);
diff --git a/mailnews/news/test/unit/test_nntpGroupPassword.js b/mailnews/news/test/unit/test_nntpGroupPassword.js
index 391e9c34f1..f612dd67fa 100644
--- a/mailnews/news/test/unit/test_nntpGroupPassword.js
+++ b/mailnews/news/test/unit/test_nntpGroupPassword.js
@@ -9,8 +9,8 @@ var daemon = setupNNTPDaemon();
 // Define these up here for checking with the transaction
 var test = null;
 
-add_task(function *() {
-  yield Services.logins.initializationPromise;
+add_task(async function () {
+  await Services.logins.initializationPromise;
 
   daemon.groupCredentials = {
     "test.subscribe.empty": ["group1", "pass1"],
diff --git a/mailnews/news/test/unit/test_nntpPassword.js b/mailnews/news/test/unit/test_nntpPassword.js
index f083253a8b..2ae365f309 100644
--- a/mailnews/news/test/unit/test_nntpPassword.js
+++ b/mailnews/news/test/unit/test_nntpPassword.js
@@ -14,9 +14,9 @@ var daemon = setupNNTPDaemon();
 // Define these up here for checking with the transaction
 var test = null;
 
-add_task(function *() {
+add_task(async function () {
   // Prepare files for passwords (generated by a script in bug 1018624).
-  yield setupForPassword("signons-mailnews1.8.json");
+  await setupForPassword("signons-mailnews1.8.json");
 
   var server = makeServer(NNTP_RFC4643_extension, daemon);
   server.start();
diff --git a/mailnews/news/test/unit/test_nntpPassword2.js b/mailnews/news/test/unit/test_nntpPassword2.js
index 7e3b6b6559..a709dbe739 100644
--- a/mailnews/news/test/unit/test_nntpPassword2.js
+++ b/mailnews/news/test/unit/test_nntpPassword2.js
@@ -17,7 +17,7 @@ var daemon = setupNNTPDaemon();
 // Define these up here for checking with the transaction
 var test = null;
 
-add_task(function *() {
+add_task(async function () {
   let server = makeServer(NNTP_RFC4643_extension, daemon);
   server.start();
 
@@ -56,7 +56,7 @@ add_task(function *() {
   Services.prefs.setCharPref("mail.server.server2.type", "nntp");
 
   // Prepare files for passwords (generated by a script in bug 1018624).
-  yield setupForPassword("signons-mailnews1.8-alt.json");
+  await setupForPassword("signons-mailnews1.8-alt.json");
 
   try {
     // Note, the uri is for hostname "invalid" which is the original uri. See
diff --git a/mailnews/news/test/unit/test_nntpPassword3.js b/mailnews/news/test/unit/test_nntpPassword3.js
index 4318d9517e..362f8e333e 100644
--- a/mailnews/news/test/unit/test_nntpPassword3.js
+++ b/mailnews/news/test/unit/test_nntpPassword3.js
@@ -14,9 +14,9 @@ var kProtocol = "nntp";
 var kHostname = "localhost";
 var kServerUrl = "news://" + kHostname;
 
-add_task(function *() {
+add_task(async function () {
   // Prepare files for passwords (generated by a script in bug 1018624).
-  yield setupForPassword("signons-mailnews1.8.json")
+  await setupForPassword("signons-mailnews1.8.json")
 
   // Set up the basic accounts and folders.
   localAccountUtils.loadLocalMailAccount();
diff --git a/mailnews/news/test/unit/test_nntpProxy.js b/mailnews/news/test/unit/test_nntpProxy.js
index 4715eee68f..71d9644520 100644
--- a/mailnews/news/test/unit/test_nntpProxy.js
+++ b/mailnews/news/test/unit/test_nntpProxy.js
@@ -9,7 +9,7 @@ const PORT = 119;
 
 var daemon, localserver, server;
 
-add_task(function* setup() {
+add_task(async function setup() {
   daemon = setupNNTPDaemon();
   server = makeServer(NNTP_RFC2980_handler, daemon);
   server.start();
@@ -17,18 +17,18 @@ add_task(function* setup() {
   localserver = setupLocalServer(PORT, "news.tinderbox.invalid");
 });
 
-add_task(function* findMessages() {
+add_task(async function findMessages() {
   // This is a trivial check that makes sure that we actually do some network
   // traffic without caring about the exact network traffic.
   let folder = localserver.rootFolder.getChildNamed("test.filter");
   equal(folder.getTotalMessages(false), 0);
   let asyncUrlListener = new PromiseTestUtils.PromiseUrlListener();
   folder.getNewMessages(null, asyncUrlListener);
-  yield asyncUrlListener.promise;
+  await asyncUrlListener.promise;
   equal(folder.getTotalMessages(false), 8);
 });
 
-add_task(function* cleanUp() {
+add_task(async function cleanUp() {
   NetworkTestUtils.shutdownServers();
   localserver.closeCachedConnections();
 });