Mailsmith AppleScripts

Compare Messages
Uses BBEdit to find the differences between two messages’ bodies.
Enter Search String and Send Now
Lets you use Command-E for both the Send Now and Enter Search String commands.
Export and Delete
Exports messages from large mailboxes and then deletes them from Mailsmith.
Forward Messages
Forwards the selected message in a single message.
Mark Mailbox Read
Marks every message in a mailbox as read (seen).
Reply to Apple Mail Message
Creates a window in Mailsmith to reply to the current Apple Mail message.
Show Unread
Shows unread messages sorted by thread.

There are also scripts for other applications.