Ocean Mail Server is a mail server with support for SMTP, POP3 and IMAP4. It offers customizable web mail, a web based remote administration interface and support for LDAP and SSL. In addition to the standard features, it includes content filtering features, ODBC support, anti-virus integration (requires third party anti-virus software), and a variety of security features to prevent abuse and spamming. Each user can have custom account settings including signatures, address book and custom anti-spam filter settings. Limited to 25 user accounts and one domain, you can purchase an unlimited user/domain version for $350.