Secure Protocols: Encrypting Mulberry
Enabling SSL in Mulberry requires two things; you must be using Mulberry version 3.x or higher and you must change one setting. If you're using an older version of Mulberry and you don't have the crypto module installed, go to the new Mulberry site and download the latest version of Mulberry, which is now free.
Once you've started Mulberry, click on File/Preferences. Make sure that you have selected Advanced mode (on the right side of the window.) Then click on the dropdown list labeled Secure: (near the bottom of the window) and select SSLv3
That's it. Now all communications between Mulberry and the IMAP server will be encrypted.