diff --git a/chat/protocols/irc/irc.js b/chat/protocols/irc/irc.js
index 6f0a9c494c..79c8cb1eff 100644
--- a/chat/protocols/irc/irc.js
+++ b/chat/protocols/irc/irc.js
@@ -317,9 +317,12 @@ var GenericIRCConversation = {
       return;
     }
 
-    // Since the server doesn't send us a message back, just assume the
-    // message was received and immediately show it.
-    this.writeMessage(this._account._nickname, aMessage, { outgoing: true });
+    // By default the server doesn't send the message back, but this can be
+    // enabled with the echo-message capability. If this is not enabled, just
+    // assume the message was received and immediately show it.
+    if (!this._account._activeCAPs.has("echo-message")) {
+      this.writeMessage(this._account._nickname, aMessage, { outgoing: true });
+    }
 
     this._pendingMessage = true;
   },
@@ -2289,6 +2292,7 @@ function ircProtocol() {
   ChromeUtils.import("resource:///modules/ircServices.jsm", tempScope);
 
   // Extra features.
+  ChromeUtils.import("resource:///modules/ircEchoMessage.jsm", tempScope);
   ChromeUtils.import("resource:///modules/ircMultiPrefix.jsm", tempScope);
   ChromeUtils.import("resource:///modules/ircNonStandard.jsm", tempScope);
   ChromeUtils.import("resource:///modules/ircSASL.jsm", tempScope);
@@ -2312,6 +2316,7 @@ function ircProtocol() {
   ircHandlers.registerCAPHandler(tempScope.capNotify);
 
   // Register extra features.
+  ircHandlers.registerCAPHandler(tempScope.capEchoMessage);
   ircHandlers.registerISUPPORTHandler(tempScope.isupportNAMESX);
   ircHandlers.registerCAPHandler(tempScope.capMultiPrefix);
   ircHandlers.registerHandler(tempScope.ircNonStandard);
diff --git a/chat/protocols/irc/ircBase.jsm b/chat/protocols/irc/ircBase.jsm
index c0a52f1377..a249664c83 100644
--- a/chat/protocols/irc/ircBase.jsm
+++ b/chat/protocols/irc/ircBase.jsm
@@ -32,7 +32,18 @@ var {
 } = ChromeUtils.import("resource:///modules/ircUtils.jsm");
 
 function privmsg(aAccount, aMessage, aIsNotification) {
-  let params = { incoming: true, tags: aMessage.tags };
+  let params = { tags: aMessage.tags };
+  // If the echo-message capability is enabled and the message is from our nick,
+  // mark it as outgoing. Otherwise, the message is incoming.
+  if (
+    aAccount._activeCAPs.has("echo-message") &&
+    aAccount.normalizeNick(aMessage.origin) ==
+      aAccount.normalizeNick(aAccount._nickname)
+  ) {
+    params.outgoing = true;
+  } else {
+    params.incoming = true;
+  }
   if (aIsNotification) {
     params.notification = true;
   }
diff --git a/chat/protocols/irc/ircEchoMessage.jsm b/chat/protocols/irc/ircEchoMessage.jsm
new file mode 100644
index 0000000000..696535571e
--- /dev/null
+++ b/chat/protocols/irc/ircEchoMessage.jsm
@@ -0,0 +1,45 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * 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/. */
+
+/*
+ * This implements the echo-message capability for IRC.
+ *   https://ircv3.net/specs/extensions/echo-message-3.2
+ *
+ * When enabled, displaying of a sent messages is disabled (until it is received
+ * by the server and sent back to the sender). This helps to ensure the ordering
+ * of messages is consistent for all participants in a channel and also helps
+ * signify whether a message was properly sent to a channel during disconnect.
+ */
+
+this.EXPORTED_SYMBOLS = ["capEchoMessage"];
+
+const { ircHandlers } = ChromeUtils.import(
+  "resource:///modules/ircHandlers.jsm"
+);
+
+var capEchoMessage = {
+  name: "echo-message CAP",
+  priority: ircHandlers.DEFAULT_PRIORITY,
+  isEnabled: () => true,
+
+  commands: {
+    "echo-message": function(aMessage) {
+      if (
+        aMessage.cap.subcommand === "LS" ||
+        aMessage.cap.subcommand === "NEW"
+      ) {
+        this.addCAP("echo-message");
+        this.sendMessage("CAP", ["REQ", "echo-message"]);
+      } else if (
+        aMessage.cap.subcommand === "ACK" ||
+        aMessage.cap.subcommand === "NAK"
+      ) {
+        this.removeCAP("echo-message");
+      } else {
+        return false;
+      }
+      return true;
+    },
+  },
+};
diff --git a/chat/protocols/irc/ircMultiPrefix.jsm b/chat/protocols/irc/ircMultiPrefix.jsm
index 30bf4a1932..61f83a8f4a 100644
--- a/chat/protocols/irc/ircMultiPrefix.jsm
+++ b/chat/protocols/irc/ircMultiPrefix.jsm
@@ -51,7 +51,7 @@ var capMultiPrefix = {
         this.addCAP("multi-prefix");
         this.sendMessage("CAP", ["REQ", "multi-prefix"]);
       } else if (
-        aMessage.cap.subcommand == "ACK" ||
+        aMessage.cap.subcommand === "ACK" ||
         aMessage.cap.subcommand === "NAK"
       ) {
         this.removeCAP("multi-prefix");
diff --git a/chat/protocols/irc/ircSASL.jsm b/chat/protocols/irc/ircSASL.jsm
index 4e7d258a4b..1d74a58415 100644
--- a/chat/protocols/irc/ircSASL.jsm
+++ b/chat/protocols/irc/ircSASL.jsm
@@ -169,11 +169,11 @@ var capSASL = {
         // If it supports SASL, let the server know we're requiring SASL.
         this.addCAP("sasl");
         this.sendMessage("CAP", ["REQ", "sasl"]);
-      } else if (aMessage.cap.subcommand == "ACK") {
+      } else if (aMessage.cap.subcommand === "ACK") {
         // The server acknowledges our choice to use SASL, send the first
         // message.
         this.sendMessage("AUTHENTICATE", "PLAIN");
-      } else if (aMessage.cap.subcommand == "NAK") {
+      } else if (aMessage.cap.subcommand === "NAK") {
         this.removeCAP("sasl");
       }
 
diff --git a/chat/protocols/irc/ircServerTime.jsm b/chat/protocols/irc/ircServerTime.jsm
index 177bd9d2bc..28df39d37e 100644
--- a/chat/protocols/irc/ircServerTime.jsm
+++ b/chat/protocols/irc/ircServerTime.jsm
@@ -4,7 +4,7 @@
 
 /*
  * This implements server-time for IRC.
- *   http://ircv3.net/specs/extensions/server-time-3.2.html
+ *   https://ircv3.net/specs/extensions/server-time-3.2.html
  */
 
 this.EXPORTED_SYMBOLS = ["capServerTime", "tagServerTime"];
@@ -52,7 +52,7 @@ var capServerTime = {
         this.addCAP("server-time");
         this.sendMessage("CAP", ["REQ", "server-time"]);
       } else if (
-        aMessage.cap.subcommand == "ACK" ||
+        aMessage.cap.subcommand === "ACK" ||
         aMessage.cap.subcommand === "NAK"
       ) {
         this.removeCAP("server-time");
@@ -71,7 +71,7 @@ var capServerTime = {
         this.addCAP("znc.in/server-time-iso");
         this.sendMessage("CAP", ["REQ", "znc.in/server-time-iso"]);
       } else if (
-        aMessage.cap.subcommand == "ACK" ||
+        aMessage.cap.subcommand === "ACK" ||
         aMessage.cap.subcommand === "NAK"
       ) {
         this.removeCAP("znc.in/server-time-iso");
diff --git a/chat/protocols/irc/moz.build b/chat/protocols/irc/moz.build
index f614fb76c5..9ac655fab9 100644
--- a/chat/protocols/irc/moz.build
+++ b/chat/protocols/irc/moz.build
@@ -16,6 +16,7 @@ EXTRA_JS_MODULES += [
     'ircCommands.jsm',
     'ircCTCP.jsm',
     'ircDCC.jsm',
+    'ircEchoMessage.jsm',
     'ircHandlers.jsm',
     'ircISUPPORT.jsm',
     'ircMultiPrefix.jsm',