OS X integration
This article lists some workarounds that might be useful in getting Thunderbird to integrate with OS X, or get applications that rely upon OS X features to work with Thunderbird.
Thunderbird doesn't have any built-in Applescript support. This can cause problems getting some OS X applications to work with it. For example, the Mail feature in iPhoto won't work with Thunderbird since iPhoto uses Applescript to communicate with email programs. iPhoto Mailer Patcher adds support for several email clients but doesn't support Thunderbird. However, iPhoto Thunderbird bridge does. 
Thunderbird 3.0 and later supports reading the OS X address book. It does not support writing it.