FTGate 

FTGate4 is a powerful Windows mail server with comprehensive Groupware functionality. Features include calendaring, contacts, IMAP, anti-spam , anti-virus support, multiple domains, Web Administration, WebMail, instant messaging, SPF,SSL + more.
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MailEnable Professional 

MailEnable Professional Edition is a enterprise level mail server for Windows 2000/NT/XP. It supports SMTP and POP3, supports an unlimited amount of email addresses, domains, groups and mailing lists.
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MailEnable Standard 

MailEnable Standard provides robust SMTP and POP3 services for Windows NT/2000/XP/2003 systems. Simple installation procedure and powerful administration tools means that you will be up and running quickly. FREE for personal and commercial use.
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MailEnable Enterprise Edition 

MailEnable Enterprise Edition is designed for organisations or ISP's dealing with high volumes of mail, requiring greater control and flexibility over mail services.
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Cactus Spam Filter 

Cactus Spam Filter is a free spam blocker. It protects your inbox by learning to detect spam as it's being used. This spam stopper integrates with all e-mail clients that use POP3 such as MS Outlook, MS Outlook Express, Netscape, Opera and Mozilla.
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MailMonitor 

MailMonitor is a program enabling you to monitor incoming and outgoing mail traffic to and from you mail server and clients. It tracks, displays and logs incoming and outgoing SMTP sessions, POP sessions and sent and received e-mails.
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