MDaemon
Download.com has some information about an interesting email server. There is a trial version that you can try out.
MDaemon, e-mail server software, contains full mail server functionality and control with a strong emphasis on security to protect your e-mail communication needs. MDaemon features include top-notch anti-spam security features; seamless integration with AntiVirus for MDaemon plug-in; built-in groupware functionalities for sharing folders, tasks, contacts, and address; separately licensed plug-in for Outlook users to access groupware functionalities using MDaemon as the mail server and groupware platform; secure instant messaging; Web-based e-mail client; remote administration tool; and central address book repository. Version 8.1 includes the first implementation of DomainKeys Identified Mail (DKIM) for the Windows platform and support for Greylisting.
From the official web site
Windows-based email server software, contains full mail server functionality and control with a strong emphasis on security to protect your email communication needs.
- Top-notch anti-spam security features
- Seamless integration with AntiVirus for MDaemon (separately licensed plug-in)
- Integrated web access email client with groupware capabilities
- Share Microsoft Outlook’s Calendar, Task, Contacts, Notes, and Journal folders via Outlook Connector for MDaemon (separately licensed plug-in)
- Secure instant messaging, web-based remote administration, and central address book repository plug-ins (see MDaemon Plug-ins page)
- MDaemon is proven as secure, dependable, and versatile.