No specific info about version 5.1. Please visit the main page of Mail on Mac Informer.
Info updated on:
Plug in for Apple Mail to generate serial mailings.
Mail Scripts is a collection of AppleScript Studio applications for Mail.
It can forward mail from AOL, Gmail, Hotmail, MSN, etc. to any e-mail address.
It is a script that creates to-do items from Mail messages.
Use Mail-Grab to extract email addresses from your Mail app or text files.