Hi there,

 This forum is for questions regarding Firefox. The links below should help you:

• Thunderbird Support homepage - http://support.mozillamessaging.com/home

• Community Forum - http://getsatisfaction.com/mozilla_messaging/

Also there is no version of Thunderbird or Firefox for the iOS.

https://wiki.mozilla.org/Mobile/Platforms#Other_Platforms iPhone/iPad/iPod

   We have no plans to release the full Firefox browser for iOS. The iOS SDK agreement requires apps to use Apple's own JavaScript engine (or none at all, like Opera Mini which downloads pre-rendered pages from Opera's servers and cannot run JavaScript code in the client). Because of this, we have no supported way to distribute Firefox's rendering and JavaScript engine to iPhone users. 
   However, you can download Firefox Home for iPhone, an iOS app that uses Firefox Sync to deliver Firefox bookmarks, browsing history, and tabs to your iPhone or iPod Touch.

For Firefox but applicable to Thunderbird also.