Email Security through Procmail (the Procmail Sanitizer) provides methods to sanitize email, removing obvious exploit attempts and disabling the channels through which exploits are delivered. Facilities for detecting and blocking Trojan Horse exploits and worms are also provided.
XamimeLT is an email scanner which encapsulates your existing sendmail or Postfix server setup. It scans both incoming and outgoing email. It can scan for email viruses, unwanted file types (eg. EXE, BMP, MPEG) and file names (eg. prettypark.exe), spam, and almost anything you care to search for in an email. It can also be used to scan for text snippets within emails and to insert disclaimers into outbound emails. XamimeLT was formerly known as "Inflex".
Perdition is a fully featured POP3 and IMAP4 proxy server. It is able to handle both SSL and non-SSL connections and redirect users to a real-server based on a database lookup. Perdition supports modular based database access. The distribution ships with modules for ODBC, MySQL, PostgreSQL, GDBM, POSIX Regular Expression, and NIS. The API for modules is open, allowing abitary modules to be written to allow access to any data store. Perdition can be used to create large mail systems where an end-user's mailbox may be stored on one of several hosts, to integrate different mail systems together, to migrate between different email infrastructures, and to bridge plain-text, SSL, and TLS services. It can also be used as part of a firewall.
ADJE WebMail is a set of Perl CGI scripts which provide a Web interface to existing email accounts on any POP3-compliant email server. The software provides a complete interface, including encoding/decoding attachments, email and URL markup in received emails, and an address book for each user.
PHP Mobile Mail is aimed at mobile professionals who want to use their favorite MUAs (noteably pine or mutt) on their laptop, either in UNIX or Windows (under GNU Gygwin). This lets you work offline. It includes a mail_spooler program, which accepts the output of you MUA and spools (on, or offline). When connected, another process parses through the spool and sends your messages. It is also designed to "fake" using your REAL email address with free services like gmx.net, or mail.yahoo.com, when using their POP and SMTP servers, assuming you have a domain and account that you can control to this degree.