diff --git a/mail/base/content/about3Pane.js b/mail/base/content/about3Pane.js
index b5fe5edd71..693bbf61c2 100644
--- a/mail/base/content/about3Pane.js
+++ b/mail/base/content/about3Pane.js
@@ -295,11 +295,11 @@ window.addEventListener("DOMContentLoaded", event => {
     }
 
     if (gFolder.isSpecialFolder(Ci.nsMsgFolderFlags.Drafts, true)) {
-      commandController.doCommand("cmd_editDraftMsg");
+      commandController.doCommand("cmd_editDraftMsg", event);
     } else if (gFolder.isSpecialFolder(Ci.nsMsgFolderFlags.Templates, true)) {
-      commandController.doCommand("cmd_newMsgFromTemplate");
+      commandController.doCommand("cmd_newMsgFromTemplate", event);
     } else {
-      commandController.doCommand("cmd_openMessage");
+      commandController.doCommand("cmd_openMessage", event);
     }
   });
 
diff --git a/mail/base/content/aboutMessage.js b/mail/base/content/aboutMessage.js
index 207ce8ece6..8a51adffb7 100644
--- a/mail/base/content/aboutMessage.js
+++ b/mail/base/content/aboutMessage.js
@@ -2,7 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, you can obtain one at http://mozilla.org/MPL/2.0/. */
 
-/* globals MailE10SUtils */
+/* globals Enigmail, MailE10SUtils */
 
 // mailCommon.js
 /* globals commandController, dbViewWrapperListener */
@@ -126,6 +126,9 @@ window.addEventListener("DOMContentLoaded", event => {
   content = document.querySelector("browser");
   OnLoadMsgHeaderPane();
 
+  Enigmail.msg.messengerStartup();
+  Enigmail.hdrView.hdrViewLoad();
+
   // The folder listener only does something interesting if this is a
   // standalone window or tab, so don't add it if we're inside about:3pane.
   if (window.browsingContext.parent.currentURI.spec != "about:3pane") {
diff --git a/mail/base/content/aboutMessage.xhtml b/mail/base/content/aboutMessage.xhtml
index 37254113c0..db149cc947 100644
--- a/mail/base/content/aboutMessage.xhtml
+++ b/mail/base/content/aboutMessage.xhtml
@@ -62,6 +62,8 @@
   <script defer="defer" src="chrome://messenger/content/editContactPanel.js"></script>
   <script defer="defer" src="chrome://messenger/content/header-fields.js"></script>
   <script defer="defer" src="chrome://messenger/content/mail-offline.js"></script>
+  <script defer="defer" src="chrome://messenger-smime/content/msgHdrViewSMIMEOverlay.js"></script>
+  <script defer="defer" src="chrome://messenger-smime/content/msgReadSMIMEOverlay.js"></script>
   <script defer="defer" src="chrome://openpgp/content/ui/enigmailMessengerOverlay.js"></script>
   <script defer="defer" src="chrome://openpgp/content/ui/enigmailMsgHdrViewOverlay.js"></script>
   <script defer="defer" src="chrome://messenger/content/msgSecurityPane.js"></script>
diff --git a/mail/extensions/openpgp/content/modules/mimeVerify.jsm b/mail/extensions/openpgp/content/modules/mimeVerify.jsm
index b00d78c21b..6c95335f2b 100644
--- a/mail/extensions/openpgp/content/modules/mimeVerify.jsm
+++ b/mail/extensions/openpgp/content/modules/mimeVerify.jsm
@@ -10,9 +10,6 @@ const EXPORTED_SYMBOLS = ["EnigmailVerify"];
  *  Module for handling PGP/MIME signed messages implemented as JS module.
  */
 
-const { MailServices } = ChromeUtils.import(
-  "resource:///modules/MailServices.jsm"
-);
 const { XPCOMUtils } = ChromeUtils.importESModule(
   "resource://gre/modules/XPCOMUtils.sys.mjs"
 );
@@ -55,7 +52,7 @@ function MimeVerify(protocol) {
 
 var EnigmailVerify = {
   _initialized: false,
-  lastMsgWindow: null,
+  lastWindow: null,
   lastMsgUri: null,
   manualMsgUri: null,
 
@@ -76,10 +73,10 @@ var EnigmailVerify = {
     }
   },
 
-  setMsgWindow(msgWindow, msgUriSpec) {
-    LOCAL_DEBUG("mimeVerify.jsm: setMsgWindow: " + msgUriSpec + "\n");
+  setWindow(window, msgUriSpec) {
+    LOCAL_DEBUG("mimeVerify.jsm: setWindow: " + msgUriSpec + "\n");
 
-    this.lastMsgWindow = msgWindow;
+    this.lastWindow = window;
     this.lastMsgUri = msgUriSpec;
   },
 
@@ -154,10 +151,9 @@ MimeVerify.prototype = {
   dataCount: 0,
   foundMsg: false,
   startMsgStr: "",
-  msgWindow: null,
+  window: null,
   msgUriSpec: null,
   statusDisplayed: false,
-  window: null,
   inStream: null,
   sigFile: null,
   sigData: "",
@@ -165,36 +161,6 @@ MimeVerify.prototype = {
 
   QueryInterface: ChromeUtils.generateQI(["nsIStreamListener"]),
 
-  startStreaming(window, msgWindow, msgUriSpec) {
-    LOCAL_DEBUG("mimeVerify.jsm: startStreaming\n");
-
-    this.msgWindow = msgWindow;
-    this.msgUriSpec = msgUriSpec;
-    this.window = window;
-    let msgSvc = MailServices.messageServiceFromURI(this.msgUriSpec);
-
-    msgSvc.streamMessage(
-      this.msgUriSpec,
-      this,
-      this.msgWindow,
-      null,
-      false,
-      null,
-      false
-    );
-  },
-
-  verifyData(window, msgWindow, msgUriSpec, data) {
-    LOCAL_DEBUG("mimeVerify.jsm: streamFromChannel\n");
-
-    this.msgWindow = msgWindow;
-    this.msgUriSpec = msgUriSpec;
-    this.window = window;
-    this.onStartRequest();
-    this.onTextData(data);
-    this.onStopRequest();
-  },
-
   parseContentType() {
     let contentTypeLine = this.mimeSvc.contentType;
 
@@ -495,7 +461,7 @@ MimeVerify.prototype = {
   onStopRequest() {
     lazy.EnigmailLog.DEBUG("mimeVerify.jsm: onStopRequest\n");
 
-    this.msgWindow = EnigmailVerify.lastMsgWindow;
+    this.window = EnigmailVerify.lastWindow;
     this.msgUriSpec = EnigmailVerify.lastMsgUri;
 
     this.backgroundJob = false;
@@ -610,8 +576,7 @@ MimeVerify.prototype = {
     }
 
     if (this.protocol === PGPMIME_PROTO) {
-      var windowManager = Services.wm;
-      var win = windowManager.getMostRecentWindow(null);
+      let win = this.window;
 
       if (!lazy.EnigmailDecryption.isReady(win)) {
         return;
@@ -678,13 +643,11 @@ MimeVerify.prototype = {
     this.mimeSvc.outputDecryptedData(data, data.length);
   },
 
-  setMsgWindow(msgWindow, msgUriSpec) {
-    lazy.EnigmailLog.DEBUG(
-      "mimeVerify.jsm: setMsgWindow: " + msgUriSpec + "\n"
-    );
+  setWindow(window, msgUriSpec) {
+    lazy.EnigmailLog.DEBUG("mimeVerify.jsm: setWindow: " + msgUriSpec + "\n");
 
-    if (!this.msgWindow) {
-      this.msgWindow = msgWindow;
+    if (!this.window) {
+      this.window = window;
       this.msgUriSpec = msgUriSpec;
     }
   },
@@ -693,7 +656,7 @@ MimeVerify.prototype = {
     lazy.EnigmailLog.DEBUG("mimeVerify.jsm: displayStatus\n");
     if (
       this.exitCode === null ||
-      this.msgWindow === null ||
+      this.window === null ||
       this.statusDisplayed ||
       this.backgroundJob
     ) {
diff --git a/mail/extensions/openpgp/content/ui/enigmailMsgHdrViewOverlay.js b/mail/extensions/openpgp/content/ui/enigmailMsgHdrViewOverlay.js
index 4ccc2572de..290f49853a 100644
--- a/mail/extensions/openpgp/content/ui/enigmailMsgHdrViewOverlay.js
+++ b/mail/extensions/openpgp/content/ui/enigmailMsgHdrViewOverlay.js
@@ -567,10 +567,7 @@ Enigmail.hdrView = {
 
         try {
           Enigmail.hdrView.statusBarHide();
-          EnigmailVerify.setMsgWindow(
-            msgWindow,
-            Enigmail.msg.getCurrentMsgUriSpec()
-          );
+          EnigmailVerify.setWindow(window, Enigmail.msg.getCurrentMsgUriSpec());
 
           let msgFrame = document.getElementById("messagepane").contentDocument;
 
@@ -600,6 +597,7 @@ Enigmail.hdrView = {
         );
 
         try {
+          EnigmailVerify.setWindow(null, null);
           Enigmail.hdrView.statusBarHide();
         } catch (ex) {}
       },
diff --git a/mail/extensions/smime/content/msgHdrViewSMIMEOverlay.js b/mail/extensions/smime/content/msgHdrViewSMIMEOverlay.js
index 1e42922303..1775df3a19 100644
--- a/mail/extensions/smime/content/msgHdrViewSMIMEOverlay.js
+++ b/mail/extensions/smime/content/msgHdrViewSMIMEOverlay.js
@@ -4,8 +4,6 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 /* import-globals-from ../../../../mailnews/extensions/smime/msgReadSMIMEOverlay.js */
-/* import-globals-from ../../../base/content/folderDisplay.js */
-/* import-globals-from ../../../base/content/mailWindow.js */
 /* import-globals-from ../../../base/content/msgHdrView.js */
 
 var gEncryptedURIService = null;
@@ -291,21 +289,22 @@ var smimeHeaderSink = {
           .GetStringFromName("CantDecryptBody")
           .replace(/%brand%/g, brand);
 
-        // insert our message
-        msgWindow.displayHTMLInMessagePane(
-          title,
-          "<html>\n" +
-            '<body bgcolor="#fafaee">\n' +
-            "<center><br><br><br>\n" +
-            "<table>\n" +
-            "<tr><td>\n" +
-            '<center><strong><font size="+3">\n' +
-            title +
-            "</font></center><br>\n" +
-            body +
-            "\n" +
-            "</td></tr></table></center></body></html>",
-          false
+        // TODO: This should be replaced with a real page, and made not ugly.
+        HideMessageHeaderPane();
+        MailE10SUtils.loadURI(
+          content,
+          "data:text/html;base64," +
+            btoa(
+              `<html>
+              <head>
+                <title>${title}</title>
+              </head>
+              <body>
+                <h1>${title}</h1>
+                ${body}
+              </body>
+            </html>`
+            )
         );
         break;
     }
@@ -386,7 +385,7 @@ function msgHdrViewSMIMEOnLoad(event) {
 
   // we want to register our security header sink as an opaque nsISupports
   // on the msgHdrSink used by mail.....
-  msgWindow.msgHeaderSink.securityInfo = smimeHeaderSink;
+  top.msgWindow.msgHeaderSink.securityInfo = smimeHeaderSink;
 
   // Add ourself to the list of message display listeners so we get notified
   // when we are about to display a message.
diff --git a/mail/test/browser/openpgp/composition/browser.ini b/mail/test/browser/openpgp/composition/browser.ini
index 1ce2dcf898..6e2fa0fba8 100644
--- a/mail/test/browser/openpgp/composition/browser.ini
+++ b/mail/test/browser/openpgp/composition/browser.ini
@@ -9,11 +9,12 @@ prefs =
   mailnews.start_page.url=about:blank
 subsuite = thunderbird
 support-files = ../data/**
-skip-if = true # TODO
 
 [browser_composeSigned.js]
-skip-if = debug # Bug 1673652 - L10NRegistry throws NS_ERROR_FILE_UNRECOGNIZED_PATH
+skip-if = true # TODO
+# skip-if = debug # Bug 1673652 - L10NRegistry throws NS_ERROR_FILE_UNRECOGNIZED_PATH
 [browser_composeEncrypted.js]
-skip-if = debug # Bug 1673652 - L10NRegistry throws NS_ERROR_FILE_UNRECOGNIZED_PATH
+skip-if = true # TODO
+# skip-if = debug # Bug 1673652 - L10NRegistry throws NS_ERROR_FILE_UNRECOGNIZED_PATH
 [browser_composeSwitchIdentity.js]
 skip-if = debug # Bug 1673652 - L10NRegistry throws NS_ERROR_FILE_UNRECOGNIZED_PATH
diff --git a/mailnews/mime/test/unit/head_mime.js b/mailnews/mime/test/unit/head_mime.js
index 33034fbc51..2b98fa336e 100644
--- a/mailnews/mime/test/unit/head_mime.js
+++ b/mailnews/mime/test/unit/head_mime.js
@@ -31,37 +31,14 @@ registerCleanupFunction(function() {
   load(gDEPTH + "mailnews/resources/mailShutdown.js");
 });
 
-function apply_mime_conversion(msgUri, headerSink = {}, msgWindow = undefined) {
-  let stubHeaderSink = {
-    securityInfo: null,
-    QueryInterface: ChromeUtils.generateQI(["nsIMsgHeaderSink"]),
-  };
-
-  // Copy the descriptors from headerSink to stubHeaderSink.
-  let fullHeaderSink = Object.create(headerSink);
-  for (let name of Object.getOwnPropertyNames(stubHeaderSink)) {
-    if (!(name in headerSink)) {
-      Object.defineProperty(
-        fullHeaderSink,
-        name,
-        Object.getOwnPropertyDescriptor(stubHeaderSink, name)
-      );
-    }
-  }
-
-  msgWindow =
-    msgWindow ||
-    Cc["@mozilla.org/messenger/msgwindow;1"].createInstance(Ci.nsIMsgWindow);
-
-  msgWindow.msgHeaderSink = fullHeaderSink;
-
+function apply_mime_conversion(msgUri, smimeHeaderSink) {
   let service = MailServices.messageServiceFromURI(msgUri);
 
   // This is what we listen on in the end.
   let listener = new PromiseTestUtils.PromiseStreamListener();
 
   // Make the underlying channel--we need this for the converter parameter.
-  let url = service.getUrlForUri(msgUri, msgWindow);
+  let url = service.getUrlForUri(msgUri);
 
   let channel = Services.io.newChannelFromURI(
     url,
diff --git a/mailnews/mime/test/unit/test_openpgp_decrypt.js b/mailnews/mime/test/unit/test_openpgp_decrypt.js
index ef7025f882..53de9d2f49 100644
--- a/mailnews/mime/test/unit/test_openpgp_decrypt.js
+++ b/mailnews/mime/test/unit/test_openpgp_decrypt.js
@@ -322,25 +322,15 @@ add_task(async function testMimeDecryptOpenPGPMessages() {
     let uri = hdr.folder.getUriForMsg(hdr);
     let sinkPromise = headerSink.expectResults(expectedResultCount);
 
-    let msgWindow = Cc["@mozilla.org/messenger/msgwindow;1"].createInstance(
-      Ci.nsIMsgWindow
-    );
-
     // Set the message window so displayStatus() invokes the hooks we are
     // interested in.
-    EnigmailVerify.lastMsgWindow = msgWindow;
+    EnigmailVerify.lastWindow = {};
 
     // Stub this function so verifyDetached() can get the correct email.
     EnigmailDecryption.getFromAddr = () => test.from;
 
     // Trigger the actual mime work.
-    let conversion = apply_mime_conversion(
-      uri,
-      {
-        securityInfo: headerSink,
-      },
-      msgWindow
-    );
+    let conversion = apply_mime_conversion(uri, headerSink);
 
     await conversion.promise;