diff --git a/mozilla/extensions/help/resources/locale/en-US/mail_help.xhtml b/mozilla/extensions/help/resources/locale/en-US/mail_help.xhtml
index d4f136b325c..2530d66ebc3 100644
--- a/mozilla/extensions/help/resources/locale/en-US/mail_help.xhtml
+++ b/mozilla/extensions/help/resources/locale/en-US/mail_help.xhtml
@@ -783,6 +783,8 @@
     address your message.</li>
   <li><strong>Check Spelling:</strong> Checks the spelling of the message text
     before you send it. You can also click Spell.</li>
+  <li><strong>Spellcheck As You Type:</strong> Choose this option to have the
+    spelling of the message text checked as you type.</li>
   <li><strong>Rewrap:</strong> If you are composing a message using the
     plain-text editor, you can use the Rewrap command to rewrap long lines of
     quoted text to fit the Compose window. This command rewraps selected quoted
@@ -4524,6 +4526,9 @@ to filter unwanted mail.</p>
   <li><strong>Check spelling before sending</strong>: Select this option to
     have Mail &amp; Newsgroups always check the spelling of your message before
     you send it.</li>
+  <li><strong>Check spelling as you type</strong>: Select this option to have
+    Mail &amp; Newsgroups always check the spelling of your message as you type
+    it.</li>
   <li><strong>For messages that contain 8-bit characters, use &apos;quoted
     printable&apos; MIME encoding</strong>: Choose to have Mail &amp;
     Newsgroups use <q>quoted printable</q> MIME encoding when sending regular
diff --git a/mozilla/mailnews/compose/prefs/resources/content/pref-composing_messages.xul b/mozilla/mailnews/compose/prefs/resources/content/pref-composing_messages.xul
index c23ce40b260..1a2641850b5 100644
--- a/mozilla/mailnews/compose/prefs/resources/content/pref-composing_messages.xul
+++ b/mozilla/mailnews/compose/prefs/resources/content/pref-composing_messages.xul
@@ -16,7 +16,7 @@
   <script type="application/x-javascript">
   <![CDATA[
     var _elementIDs = ["forwardMessageMode", "autoSave",
-                       "autoSaveInterval","spellCheckBeforeSend",
+                       "autoSaveInterval","spellCheckBeforeSend", "inlineSpellCheck",
                        "strictlyMime", "mailWarnOnSendAccelKey",
                        "wrapLength", "sendDefaultCharsetList",
                        "replyInDefaultCharset", "FontSelect",
@@ -28,8 +28,9 @@
 
     function Startup()
     {
-      document.getElementById("spellCheckBeforeSend").hidden =
-        !("@mozilla.org/spellchecker;1" in Components.classes);
+      var hideSpellCheck = !("@mozilla.org/spellchecker;1" in Components.classes);
+      document.getElementById("spellCheckBeforeSend").hidden = hideSpellCheck;
+      document.getElementById("inlineSpellCheck").hidden = hideSpellCheck;
       gAutoSaveInterval = document.getElementById("autoSaveInterval");
       enableTextbox(document.getElementById("autoSave"), gAutoSaveInterval, true);
     }
@@ -86,11 +87,17 @@
                 prefstring="mail.compose.autosaveinterval"/>
       <label value="&autoSaveEnd.label;"/>
     </hbox>
-    
-    <checkbox id="spellCheckBeforeSend" label="&spellCheck.label;"
-              prefstring="mail.SpellCheckBeforeSend"
-              accesskey="&spellCheck.accesskey;"/>
-  
+
+    <hbox align="center">
+      <checkbox id="spellCheckBeforeSend" label="&spellCheck.label;"
+                prefstring="mail.SpellCheckBeforeSend"
+                accesskey="&spellCheck.accesskey;"/>
+
+      <checkbox id="inlineSpellCheck" label="&spellCheckInline.label;"
+                prefstring="mail.spellcheck.inline"
+                accesskey="&spellCheckInline.accesskey;"/>
+    </hbox>
+
     <checkbox id="strictlyMime" label="&useMIME.label;"
               prefstring="mail.strictly_mime"
               accesskey="&useMIME.accesskey;"/>
@@ -100,7 +107,7 @@
                 prefstring="mail.warn_on_send_accel_key"
                 accesskey="&warnOnSendAccelKey.accesskey;" />
     </hbox>
-    
+
 	<hbox align="center">
         <label value="&wrapOutMsg.label;" accesskey="&wrapOutMsg.accesskey;" control="wrapLength"/>
     <textbox id="wrapLength" size="3" preftype="int"
diff --git a/mozilla/mailnews/compose/prefs/resources/locale/en-US/pref-composing_messages.dtd b/mozilla/mailnews/compose/prefs/resources/locale/en-US/pref-composing_messages.dtd
index 774ab508b0d..0a77bd4ef95 100644
--- a/mozilla/mailnews/compose/prefs/resources/locale/en-US/pref-composing_messages.dtd
+++ b/mozilla/mailnews/compose/prefs/resources/locale/en-US/pref-composing_messages.dtd
@@ -55,6 +55,8 @@
 <!ENTITY autoSaveEnd.label                    "minutes">
 <!ENTITY spellCheck.label                     "Check spelling before sending">
 <!ENTITY spellCheck.accesskey                 "C">
+<!ENTITY spellCheckInline.label               "Check spelling as you type">
+<!ENTITY spellCheckInline.accesskey           "e">
 <!-- LOCALIZATION NOTE (wrapOutMsg.label): This will concatenate with "xxx characters", using a number and (char.label). -->
 <!ENTITY wrapOutMsg.label                     "Wrap plain text messages at">
 <!ENTITY wrapOutMsg.accesskey                 "W">
diff --git a/mozilla/mailnews/compose/resources/content/MsgComposeCommands.js b/mozilla/mailnews/compose/resources/content/MsgComposeCommands.js
index dff327878a6..4f44cb63174 100644
--- a/mozilla/mailnews/compose/resources/content/MsgComposeCommands.js
+++ b/mozilla/mailnews/compose/resources/content/MsgComposeCommands.js
@@ -21,6 +21,7 @@
  * the Initial Developer. All Rights Reserved.
  *
  * Contributor(s):
+ *   Ian Neal <bugzilla@arlen.demon.co.uk>
  *
  * Alternatively, the contents of this file may be used under the terms of
  * either of the GNU General Public License Version 2 or later (the "GPL"),
@@ -606,6 +607,25 @@ function updateComposeItems() {
   } catch(e) {}
 }
 
+function openEditorContextMenu()
+{
+  // if we have a mispelled word, show spellchecker context
+  // menuitems as well as 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");
@@ -1285,6 +1305,8 @@ 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) 
@@ -1347,8 +1369,7 @@ function ComposeStartup(recycled, aParams)
 
       if (recycled)
       {
-        // This sets charset and does reply quote insertion
-        gMsgCompose.initEditor(GetCurrentEditor(), window.content);
+        InitEditor(GetCurrentEditor());
 
         if (gMsgCompose.composeHTML)
         {
@@ -1395,7 +1416,7 @@ var gMsgEditorCreationObserver =
     {
       var editor = GetCurrentEditor();
       if (editor && GetCurrentCommandManager() == aSubject)
-        gMsgCompose.initEditor(editor, window.content);
+        InitEditor(editor);
     }
   }
 }
@@ -1998,6 +2019,43 @@ function SelectAddress()
   AdjustFocus();
 }
 
+// walk through the recipients list and add them to the inline spell checker ignore list
+function addRecipientsToIgnoreList(aAddressesToAdd)
+{
+  if (InlineSpellChecker.inlineSpellChecker && InlineSpellChecker.inlineSpellChecker.enableRealTimeSpell)
+  {
+    // break the list of potentially many recipients back into individual names
+    var hdrParser = Components.classes["@mozilla.org/messenger/headerparser;1"].getService(Components.interfaces.nsIMsgHeaderParser);
+    var emailAddresses = {};
+    var names = {};
+    var fullNames = {};
+    var numAddresses = hdrParser.parseHeadersWithArray(aAddressesToAdd, emailAddresses, names, fullNames);
+    var tokenizedNames = [];
+
+    // each name could consist of multiple words delimited by commas and/or spaces.
+    // i.e. Green Lantern or Lantern,Green.
+    for (var i = 0; i < names.value.length; i++)
+    {
+      var splitNames = names.value[i].match(/[^\s,]+/g);
+      if (splitNames)
+        tokenizedNames = tokenizedNames.concat(splitNames);
+    }
+
+    InlineSpellChecker.inlineSpellChecker.ignoreWords(tokenizedNames, tokenizedNames.length);
+  }
+}
+
+function ToggleInlineSpellChecker(target)
+{
+  if (InlineSpellChecker.inlineSpellChecker)
+  {
+    InlineSpellChecker.inlineSpellChecker.enableRealTimeSpell = !InlineSpellChecker.inlineSpellChecker.enableRealTimeSpell;
+
+    if (InlineSpellChecker.inlineSpellChecker.enableRealTimeSpell)
+      InlineSpellChecker.checkDocument(window.content.document);
+  }
+}
+
 function ToggleReturnReceipt(target)
 {
     var msgCompFields = gMsgCompose.compFields;
@@ -2644,6 +2702,9 @@ function LoadIdentity(startup)
               // catch the exception and ignore it, so that if LDAP setup 
               // fails, the entire compose window doesn't end up horked
           }
+
+          // only do this if we aren't starting up....it gets done as part of startup already
+          addRecipientsToIgnoreList(gCurrentIdentity.identityName);
       }
     }
 }
@@ -3061,3 +3122,16 @@ function AutoSave()
   gAutoSaveTimeout = setTimeout(AutoSave, gAutoSaveInterval);
 }
 
+function InitEditor(editor)
+{
+  gMsgCompose.initEditor(editor, window.content);
+  try {
+    InlineSpellChecker.Init(editor, sPrefs.getBoolPref("mail.spellcheck.inline"));
+    // Following line works round bug 292520, look at removing after that is fixed
+    InlineSpellChecker.checkDocument(window.content.document);
+  } catch (e) {
+    // InlineSpellChecker.Init throws if there is no inline spellchecker
+    // so disable menuitem.
+    document.getElementById('menu_inlineSpellCheck').setAttribute('disabled', true);
+  }
+}
diff --git a/mozilla/mailnews/compose/resources/content/addressingWidgetOverlay.js b/mozilla/mailnews/compose/resources/content/addressingWidgetOverlay.js
index 988dad86aaf..6da7dd27c7d 100644
--- a/mozilla/mailnews/compose/resources/content/addressingWidgetOverlay.js
+++ b/mozilla/mailnews/compose/resources/content/addressingWidgetOverlay.js
@@ -19,6 +19,7 @@
  * the Initial Developer. All Rights Reserved.
  *
  * Contributor(s):
+ *   Ian Neal <bugzilla@arlen.demon.co.uk>
  *
  * Alternatively, the contents of this file may be used under the terms of
  * either of the GNU General Public License Version 2 or later (the "GPL"),
@@ -57,6 +58,7 @@ var gMimeHeaderParser = null;
  */
 
 var test_addresses_sequence = false;
+
 try {
   if (sPrefs)
     test_addresses_sequence = sPrefs.getBoolPref("mail.debug.test_addresses_sequence");
@@ -238,6 +240,10 @@ function CompFields2Recipients(msgCompFields, msgType)
     parent.replaceChild(newListBoxNode, listbox);
     awFitDummyRows(2);
 
+    // CompFields2Recipients is called whenever a user replies or edits an existing message.
+    // We want to add all of the recipients for this message to the ignore list for spell check 
+    addRecipientsToIgnoreList((gCurrentIdentity ? gCurrentIdentity.identityName + ', ' : '') + msgTo + ', ' + msgCC + ', ' + msgBCC);
+
     gMimeHeaderParser = null; //Release the mime parser
   }
 }
@@ -365,6 +371,9 @@ function awAddRecipient(recipientType, address)
     awAppendNewRow(true);
     awSetInputAndPopupValue(awGetInputElement(top.MAX_RECIPIENTS), "", awGetPopupElement(top.MAX_RECIPIENTS), "addr_to", top.MAX_RECIPIENTS);
   }
+
+  // add the recipient to our spell check ignore list
+  addRecipientsToIgnoreList(address);
 }
 
 function awTestRowSequence()
@@ -491,6 +500,10 @@ function awReturnHit(inputElement)
     nextInput.select();
     awSetFocus(row+1, nextInput);
   }
+
+  // be sure to add the recipient to our ignore list
+  // when the user hits enter in an autocomplete widget...
+  addRecipientsToIgnoreList(inputElement.value);
 }
 
 function awDeleteHit(inputElement)
@@ -725,7 +738,7 @@ function _awSetFocus()
 
 function awTabFromRecipient(element, event)
 {
-  //If we are le last element in the listbox, we don't want to create a new row.
+  //If we are the last element in the listbox, we don't want to create a new row.
   if (element == awGetInputElement(top.MAX_RECIPIENTS))
     top.doNotCreateANewRow = true;
 
@@ -735,6 +748,10 @@ function awTabFromRecipient(element, event)
     var listBox = document.getElementById("addressingWidget");
     listBox.listBoxObject.ensureIndexIsVisible(listBoxRow + 1);
   }
+
+  // be sure to add the recipient to our ignore list
+  // when the user tabs out of an autocomplete line...
+  addRecipientsToIgnoreList(element.value);
 }
 
 function awTabFromMenulist(element, event)
diff --git a/mozilla/mailnews/compose/resources/content/messengercompose.xul b/mozilla/mailnews/compose/resources/content/messengercompose.xul
index 3d7d6c8035a..e33a33a4e17 100644
--- a/mozilla/mailnews/compose/resources/content/messengercompose.xul
+++ b/mozilla/mailnews/compose/resources/content/messengercompose.xul
@@ -24,6 +24,7 @@
    -   Ben Goodger <ben@netscape.com> (ass'td polish fixes)
    -   Håkan Waara <hwaara@chello.se>
    -   Neil Rashbrook <neil@parkwaycc.co.uk> (ass'td polish fix)
+   -   Ian Neal <bugzilla@arlen.demon.co.uk>
    -
    - Alternatively, the contents of this file may be used under the terms of
    - either of the GNU General Public License Version 2 or later (the "GPL"),
@@ -93,6 +94,7 @@
 <script type="application/x-javascript" src="chrome://messenger/content/widgetglue.js"/>
 <script type="application/x-javascript" src="chrome://messenger/content/mail-offline.js"/>
 <script type="application/x-javascript" src="chrome://editor/content/editor.js"/>
+<script type="application/x-javascript" src="chrome://editor/content/editorInlineSpellCheck.js"/>
 <script type="application/x-javascript" src="chrome://messenger/content/messengercompose/MsgComposeCommands.js"/>
 
 <!-- drag and drop -->
@@ -208,7 +210,16 @@
 <keyset id="editorKeys"/>
 
 <popup id="sidebarPopup"/>
-<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"/>
@@ -329,6 +340,9 @@
         <menupopup id="optionsMenuPopup" onpopupshowing="updateOptionItems();"> 
           <menuitem label="&selectAddressCmd.label;" accesskey="&selectAddressCmd.accesskey;" command="cmd_selectAddress"/>
           <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;" 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/mozilla/mailnews/compose/resources/locale/en-US/messengercompose.dtd b/mozilla/mailnews/compose/resources/locale/en-US/messengercompose.dtd
index ff353e09282..4b1d27715e4 100644
--- a/mozilla/mailnews/compose/resources/locale/en-US/messengercompose.dtd
+++ b/mozilla/mailnews/compose/resources/locale/en-US/messengercompose.dtd
@@ -117,7 +117,9 @@
 
 <!ENTITY checkSpellingCmd.label "Check Spelling...">
 <!ENTITY checkSpellingCmd.key "K">
-<!ENTITY checkSpellingCmd.accesskey "S">
+<!ENTITY checkSpellingCmd.accesskey "h">
+<!ENTITY enableInlineSpellChecker.label "Spellcheck As You Type">
+<!ENTITY enableInlineSpellChecker.accesskey "S">
 
 <!ENTITY priorityMenu.label "Priority">
 <!ENTITY priorityMenu.accesskey "p">
@@ -197,6 +199,11 @@
 <!ENTITY formatToolbar.underlineChar "U">
 
 <!-- context menu items -->
+<!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">
diff --git a/mozilla/mailnews/mailnews.js b/mozilla/mailnews/mailnews.js
index 91416b9ec44..72513eb3031 100644
--- a/mozilla/mailnews/mailnews.js
+++ b/mozilla/mailnews/mailnews.js
@@ -510,6 +510,7 @@ pref("mailnews.nav_crosses_folders", 1); // prompt user when crossing folders
 pref("news.cancel.confirm",true);
 pref("news.cancel.alert_on_success",true);
 pref("mail.SpellCheckBeforeSend",false);
+pref("mail.spellcheck.inline",true);
 pref("mail.warn_on_send_accel_key", true);
 pref("mail.enable_autocomplete",true);
 pref("mailnews.html_domains","");