Anti-Spam SMTP Proxy Server implements multiple spam filters
Strong Email & Apache Log Analysis with Active Security Features
Booking/reservation of meeting rooms/equipment with e-mail invitations
Google Apps Script to send third party recruiter email to spam
Unified Communications Server
an 'auto-reply' bot for your mail server
The free cross-platform antivirus software tool-kit
Free and open source webmail software
Source code for be able to use Relation Tags.
File sharing via e-mail