Comment 75 for bug 603402

(In reply to Nye Liu from comment #36)
> Would it be possible to at least add some sort of menu option next to "work offline" ... like "force sync" or something?

A possible way.
- Install "Custom Buttons" addon, add your own Toolbar Button labeled "force sync".
- Put small JavaScript code like "click Work Offline, reply if required, wait for a while, click Work Online, reply if required".
  /*CODE*/
  // var MenuId="goOfflineMenuitem" ; // Firefox
      var MenuId="goOfflineMenuItem" ; // Thunderbird
      var Menu=document.getElementById(MenuId) ;
      var Status=( "true" == Menu.getAttribute("checked") ) ; // atribute value is String
      var OnCommand=Menu.getAttribute("oncommand") ;
      // oncommand="MailOfflineMgr.toggleOfflineStatus();"
      if( false == Status )
      {
          // go Work Offline
          eval(OnCommand);
          // do reply to dialog for download now,
          // go back Work Online, and do reply to dialog for send unsent messages
          // setTimeout(GoBackOnline,3*1000) ;
       }
      else if( true == Status )
      {
         // go back Work Online
         eval(OnCommand);
         // and do reply to dialog for send unsent messages
      }

This version doesn't do automatic reply to confirmtion dialog, doesn't do Toogle Back to Work Online mode.
So, you have to do: 1. Click the button, 2. No to dialog(download now), 3. click button, 4. Cancel to dialog(send unsent mail).
This is merely an example of your own pretty small Addon by your own ToolBar button.
id of menuitem, toolbarbutton , attributes of them etc. can be pretty easily known using DOM Inspector.