diff --git a/mail/app/profile/all-thunderbird.js b/mail/app/profile/all-thunderbird.js
index 31d7fe7c4927..70e783b29792 100644
--- a/mail/app/profile/all-thunderbird.js
+++ b/mail/app/profile/all-thunderbird.js
@@ -109,6 +109,7 @@ pref("update.severity", 0);
 pref("xpinstall.whitelist.add", "update.mozilla.org,addons.mozilla.org");
 
 pref("mail.phishing.detection.enabled", true); // enable / disable phishing detection for link clicks
+pref("mail.spellcheck.inline", false);
 
 /////////////////////////////////////////////////////////////////
 // Overrides of the seamonkey suite mailnews.js prefs
diff --git a/mail/components/compose/content/MsgComposeCommands.js b/mail/components/compose/content/MsgComposeCommands.js
index 13e1a946f279..defe25ef8629 100644
--- a/mail/components/compose/content/MsgComposeCommands.js
+++ b/mail/components/compose/content/MsgComposeCommands.js
@@ -571,7 +571,6 @@ function GetSelectedMessages()
 
 function SetupCommandUpdateHandlers()
 {
-//  dump("SetupCommandUpdateHandlers\n");
   top.controllers.insertControllerAt(0, defaultController);
 }
 
@@ -592,37 +591,57 @@ function CommandUpdate_MsgCompose()
   updateComposeItems();
 }
 
-function updateComposeItems() {
-  try {
-
-  //Edit Menu
-  goUpdateCommand("cmd_rewrap");
-
-  //Insert Menu
-  if (gMsgCompose && gMsgCompose.composeHTML)
+function updateComposeItems() 
+{
+  try 
   {
-    goUpdateCommand("cmd_renderedHTMLEnabler");
-    goUpdateCommand("cmd_decreaseFont");
-    goUpdateCommand("cmd_increaseFont");
-    goUpdateCommand("cmd_bold");
-    goUpdateCommand("cmd_italic");
-    goUpdateCommand("cmd_underline");
-    goUpdateCommand("cmd_ul");
-    goUpdateCommand("cmd_ol");
-    goUpdateCommand("cmd_indent");
-    goUpdateCommand("cmd_outdent");
-    goUpdateCommand("cmd_align");
-    goUpdateCommand("cmd_smiley");
-  }
+    //Edit Menu
+    goUpdateCommand("cmd_rewrap");
 
-  //Options Menu
-  goUpdateCommand("cmd_spelling");
-  goUpdateCommand("cmd_quoteMessage");
+    //Insert Menu
+    if (gMsgCompose && gMsgCompose.composeHTML)
+    {
+      goUpdateCommand("cmd_renderedHTMLEnabler");
+      goUpdateCommand("cmd_decreaseFont");
+      goUpdateCommand("cmd_increaseFont");
+      goUpdateCommand("cmd_bold");
+      goUpdateCommand("cmd_italic");
+      goUpdateCommand("cmd_underline");
+      goUpdateCommand("cmd_ul");
+      goUpdateCommand("cmd_ol");
+      goUpdateCommand("cmd_indent");
+      goUpdateCommand("cmd_outdent");
+      goUpdateCommand("cmd_align");
+      goUpdateCommand("cmd_smiley");
+    }
+
+    //Options Menu
+    goUpdateCommand("cmd_spelling");
+    goUpdateCommand("cmd_quoteMessage");
 
   } catch(e) {}
 }
 
-function updateEditItems() {
+function openEditorContextMenu() 
+{
+  // if we have a mispelled word, do one thing, otherwise show the usual context menu
+  var spellCheckNoSuggestionsItem = document.getElementById('spellCheckNoSuggestions');
+  var word;
+  var misspelledWordStatus = InlineSpellChecker.updateSuggestionsMenu(document.getElementById('msgComposeContext'), spellCheckNoSuggestionsItem,
+                              word);
+  
+  var hideSpellingItems = (misspelledWordStatus == kSpellNoMispelling);
+  spellCheckNoSuggestionsItem.hidden = hideSpellingItems || misspelledWordStatus != kSpellNoSuggestionsFound;
+  document.getElementById('spellCheckAddToDictionary').hidden = hideSpellingItems;
+  document.getElementById('spellCheckIgnoreWord').hidden = hideSpellingItems;
+  document.getElementById('spellCheckAddSep').hidden = hideSpellingItems;
+  document.getElementById('spellCheckSuggestionsSeparator').hidden = hideSpellingItems;
+
+  updateEditItems();
+}
+
+function updateEditItems() 
+{
   goUpdateCommand("cmd_pasteNoFormatting");
   goUpdateCommand("cmd_pasteQuote");
   goUpdateCommand("cmd_delete");
@@ -633,8 +652,10 @@ function updateEditItems() {
   goUpdateCommand("cmd_findPrev");
 }
 
-var messageComposeOfflineObserver = {
-  observe: function(subject, topic, state) {
+var messageComposeOfflineObserver = 
+{
+  observe: function(subject, topic, state) 
+  {
     // sanity checks
     if (topic != "network:offline-status-changed") return;
     if (state == "offline")
@@ -1289,6 +1310,7 @@ function ComposeStartup(recycled, aParams)
                                          gMsgCompose.compFields.returnReceipt);
       document.getElementById("cmd_attachVCard").setAttribute('checked', 
                                          gMsgCompose.compFields.attachVCard);
+      document.getElementById("menu_inlineSpellCheck").setAttribute('checked', sPrefs.getBoolPref("mail.spellcheck.inline"));
 
       // If recycle, editor is already created
       if (!recycled) 
@@ -1357,8 +1379,7 @@ function ComposeStartup(recycled, aParams)
 
       if (recycled)
       {
-        // This sets charset and does reply quote insertion
-        gMsgCompose.initEditor(GetCurrentEditor(), window.content);
+        InitEditor();
 
         if (gMsgCompose.composeHTML)
         {
@@ -1419,7 +1440,7 @@ var gMsgEditorCreationObserver =
       {
         var editorStyle = editor.QueryInterface(Components.interfaces.nsIEditorStyleSheets);
         editorStyle.addStyleSheet("chrome://messenger/skin/messageQuotes.css");
-        gMsgCompose.initEditor(editor, window.content);
+        InitEditor();
       }
     }
   }
@@ -2020,7 +2041,6 @@ function SelectAddress()
   var ccAddress = msgCompFields.cc;
   var bccAddress = msgCompFields.bcc;
 
-  dump("toAddress: " + toAddress + "\n");
   window.openDialog("chrome://messenger/content/addressbook/abSelectAddressesDialog.xul",
             "",
             "chrome,resizable,titlebar,modal",
@@ -2034,6 +2054,18 @@ function SelectAddress()
   AdjustFocus();
 }
 
+function ToggleInlineSpellChecker(target)
+{
+  if (InlineSpellChecker.inlineSpellChecker)
+  {
+    InlineSpellChecker.inlineSpellChecker.enableRealTimeSpell = !InlineSpellChecker.inlineSpellChecker.enableRealTimeSpell;
+    target.setAttribute('checked', InlineSpellChecker.inlineSpellChecker.enableRealTimeSpell);
+
+    if (InlineSpellChecker.inlineSpellChecker.enableRealTimeSpell)
+      InlineSpellChecker.checkDocument(window.content.document);
+  }
+}
+
 function ToggleReturnReceipt(target)
 {
     var msgCompFields = gMsgCompose.compFields;
@@ -2047,13 +2079,13 @@ function ToggleReturnReceipt(target)
 
 function ToggleAttachVCard(target)
 {
-    var msgCompFields = gMsgCompose.compFields;
-    if (msgCompFields)
-    {
-        msgCompFields.attachVCard = ! msgCompFields.attachVCard;
-        target.setAttribute('checked', msgCompFields.attachVCard);
-        gAttachVCardOptionChanged = true;
-    }
+  var msgCompFields = gMsgCompose.compFields;
+  if (msgCompFields)
+  {
+    msgCompFields.attachVCard = ! msgCompFields.attachVCard;
+    target.setAttribute('checked', msgCompFields.attachVCard);
+    gAttachVCardOptionChanged = true;
+  }
 }
 
 function queryISupportsArray(supportsArray, iid) {
@@ -3302,3 +3334,10 @@ function AutoSave()
   gAutoSaveTimeout = setTimeout("AutoSave()", gAutoSaveInterval);
 }
 
+function InitEditor()
+{
+  var editor = GetCurrentEditor();
+  gMsgCompose.initEditor(editor, window.content);
+  InlineSpellChecker.Init(editor, sPrefs.getBoolPref("mail.spellcheck.inline"));
+  InlineSpellChecker.checkDocument(window.content.document);
+}
diff --git a/mail/components/compose/content/messengercompose.xul b/mail/components/compose/content/messengercompose.xul
index 5928f075ce03..b9d6b7df9f81 100644
--- a/mail/components/compose/content/messengercompose.xul
+++ b/mail/components/compose/content/messengercompose.xul
@@ -70,6 +70,7 @@
 </stringbundleset>
 
 <script type="application/x-javascript" src="chrome://communicator/content/printing.js"/>
+<script type="application/x-javascript" src="chrome://editor/content/editorInlineSpellCheck.js"/>
 <script type="application/x-javascript" src="chrome://messenger/content/accountUtils.js"/>
 <script type="application/x-javascript" src="chrome://messenger/content/widgetglue.js"/>
 <script type="application/x-javascript" src="chrome://messenger/content/mailCore.js"/>
@@ -234,9 +235,18 @@
 
 <keyset id="editorKeys"/>
 
-<popup id="msgComposeContext" onpopupshowing="updateEditItems();">
+<popup id="msgComposeContext"
+    onpopupshowing="openEditorContextMenu();">
+  
+  <menuitem id="spellCheckNoSuggestions" label="&spellCheckNoSuggestions.label;" disabled="true"/>
+  <menuseparator id="spellCheckAddSep"/>
+  <menuitem id="spellCheckAddToDictionary" label="&spellCheckAddToDictionary.label;" accesskey="&spellCheckAddToDictionary.accesskey;"
+            oncommand="InlineSpellChecker.addToDictionary(null,null);"/>  
+  <menuitem id="spellCheckIgnoreWord" label="&spellCheckIgnoreWord.label;" accesskey="&spellCheckIgnoreWord.accesskey;"
+            oncommand="InlineSpellChecker.ignoreWord(null, null)"/>  
+  <menuseparator id="spellCheckSuggestionsSeparator"/>
+
   <menuitem label="&undo.label;" accesskey="&undo.accesskey;" command="cmd_undo"/>
-  <menuseparator/>
   <menuitem label="&cut.label;" accesskey="&cut.accesskey;" command="cmd_cut"/>
   <menuitem label="&copy.label;" accesskey="&copy.accesskey;" command="cmd_copy"/>
   <menuitem label="&paste.label;" accesskey="&paste.accesskey;" command="cmd_paste"/>
@@ -394,6 +404,9 @@
       <menu id="optionsMenu" label="&optionsMenu.label;" accesskey="&optionsMenu.accesskey;">
         <menupopup id="optionsMenuPopup"> 
           <menuitem label="&checkSpellingCmd.label;" id="menu_checkspelling" accesskey="&checkSpellingCmd.accesskey;" key="key_checkspelling" command="cmd_spelling"/>
+          <menuitem label="&enableInlineSpellChecker.label;" id="menu_inlineSpellCheck" 
+                           accesskey="&enableInlineSpellChecker.accesskey;" checked="false"
+                           type="checkbox" oncommand="ToggleInlineSpellChecker(event.target)"/>
           <menuitem label="&quoteCmd.label;" accesskey="&quoteCmd.accesskey;" command="cmd_quoteMessage"/>
           <menuseparator/>
           <menuitem id="returnReceiptMenu" type="checkbox" label="&returnReceiptMenu.label;" accesskey="&returnReceiptMenu.accesskey;" checked="false" oncommand="ToggleReturnReceipt(event.target)"/>
diff --git a/mail/components/prefwindow/content/pref-composing_messages.xul b/mail/components/prefwindow/content/pref-composing_messages.xul
index dd1684215c0b..9d643f83bf35 100644
--- a/mail/components/prefwindow/content/pref-composing_messages.xul
+++ b/mail/components/prefwindow/content/pref-composing_messages.xul
@@ -12,7 +12,7 @@
 
   <script type="application/x-javascript">
     <![CDATA[
-      var _elementIDs = ["forwardMessageMode", "spellCheckBeforeSend", "strictlyMime", 
+      var _elementIDs = ["forwardMessageMode", "spellCheckBeforeSend", "inlineSpellCheck", "strictlyMime", 
                          "wrapLength", "mailWarnOnSendAccelKey", "autoSave", 
                          "autoSaveInterval",
                          // auto complete prefs 
@@ -28,6 +28,7 @@
       function Startup()
       {
         document.getElementById("spellCheckBeforeSend").hidden =! ("@mozilla.org/spellchecker;1" in Components.classes);
+        document.getElementById("inlineSpellCheck").hidden =! ("@mozilla.org/spellchecker;1" in Components.classes);
 
         // autocomplete
         enableAutocomplete();
@@ -72,6 +73,10 @@
               prefstring="mail.SpellCheckBeforeSend"
               accesskey="&spellCheck.accesskey;"/>
   
+    <checkbox id="inlineSpellCheck" label="&spellCheckInline.label;"
+              prefstring="mail.spellcheck.inline"
+              accesskey="&spellCheckInline.accesskey;"/>
+  
     <checkbox id="strictlyMime" label="&useMIME.label;"
               prefstring="mail.strictly_mime"
               accesskey="&useMIME.accesskey;"/>
diff --git a/mail/locales/en-US/chrome/messenger/messengercompose/messengercompose.dtd b/mail/locales/en-US/chrome/messenger/messengercompose/messengercompose.dtd
index 6b9c6cbcfbf6..0378db593794 100644
--- a/mail/locales/en-US/chrome/messenger/messengercompose/messengercompose.dtd
+++ b/mail/locales/en-US/chrome/messenger/messengercompose/messengercompose.dtd
@@ -119,7 +119,9 @@
 <!ENTITY checkSpellingCmd.label "Check Spelling...">
 <!ENTITY checkSpellingCmd.key "K">
 <!ENTITY checkSpellingCmd.key2 "VK_F7">
-<!ENTITY checkSpellingCmd.accesskey "S">
+<!ENTITY checkSpellingCmd.accesskey "h">
+<!ENTITY enableInlineSpellChecker.label "Spell As You Type">
+<!ENTITY enableInlineSpellChecker.accesskey "S">
 <!ENTITY quoteCmd.label "Quote Message">
 <!ENTITY quoteCmd.accesskey "Q">
 
@@ -251,6 +253,11 @@
 <!ENTITY smiley16Cmd.label "Lips-are-Sealed">
 
 <!-- Message Pane Context Menu -->
+<!ENTITY spellCheckNoSuggestions.label "No Suggestions Found">
+<!ENTITY spellCheckIgnoreWord.label "Ignore Word">
+<!ENTITY spellCheckIgnoreWord.accesskey "I">
+<!ENTITY spellCheckAddToDictionary.label "Add to Dictionary">
+<!ENTITY spellCheckAddToDictionary.accesskey "n">
 <!ENTITY undo.label "Undo">
 <!ENTITY undo.accesskey "U">
 <!ENTITY cut.label "Cut">
@@ -275,3 +282,4 @@
 
 <!-- Title for the address picker panel -->
 <!ENTITY addressesSidebarTitle.label "Contacts">
+
diff --git a/mail/locales/en-US/chrome/messenger/messengercompose/pref-composing_messages.dtd b/mail/locales/en-US/chrome/messenger/messengercompose/pref-composing_messages.dtd
index 78c6a83006b3..f8970849292b 100644
--- a/mail/locales/en-US/chrome/messenger/messengercompose/pref-composing_messages.dtd
+++ b/mail/locales/en-US/chrome/messenger/messengercompose/pref-composing_messages.dtd
@@ -11,6 +11,8 @@
 <!ENTITY sendingMessagesHeader.label          "Composing Messages">
 <!ENTITY spellCheck.label                     "Check spelling before sending">
 <!ENTITY spellCheck.accesskey                 "c">
+<!ENTITY spellCheckInline.label               "Enable spell as you type">
+<!ENTITY spellCheckInline.accesskey           "n">
 <!ENTITY useMIME.label                        "For messages that contain 8-bit characters, use 'quoted printable' MIME encoding. Leave unchecked to send the messages as is.">
 <!ENTITY useMIME.accesskey                    "o">
 <!ENTITY warnOnSendAccelKey.label             "Confirm when using keyboard shortcut to send message">