New features in this version:
-Group permissions which allow you to control several features.
-Security features such as "lock to xoops" which will prevent spammers and abuse on your server.
-User created webmail. Now you can list, erase and change mail quotas for your user@myserver.com accounts.
-New smtp class. This new class works with the vast majority of mail servers. It allows for multiple authentication methods.
-Attachments are now sent directly from users computer. No more worring about temporary files on your server.
-Integrated Help. Now you can access a help file from the admin menu with a detailed explanation of what each option does.

More infos on the official project pages:
http://dev.xoops.org/modules/xfmod/project/?group_id=1132