E-mail filter designed to protect Windows clients
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Introduced in June, 2000, MIMEDefang is a robust e-mail filter designed to protect Windows clients from mail-borne viruses and trojans. It has become the leading Milter worldwide, but MIMEDefang is intended for experienced Linux administrators.

MIMEDefang also powers our CanIt™ enterprise anti spam solution, which is designed for everyone, including novice users.

Mail Inspection and Modification

MIMEDefang can inspect and modify e-mail messages as they pass through your mail relay. MIMEDefang is written in Perl, and its filter actions are expressed in Perl, so it's highly flexible. Here are some things that you can do very easily with MIMEDefang:

  • Delete or alter attachments based on file name, contents, results of a virus scan, attachment size, etc.
  • Replace large attachments with links to a centrally-stored copy to ease the burden on POP3 users with slow modem links.
  • Add boilerplate text to e-mail messages.
  • Customize filter rules based on domain, user-name, relay machine, etc.
  • Reject unacceptable messages, where you define what "unacceptable" means.
  • Add or delete recipients for a message.

Download or Contribute to MIMEDefang

Find out more about MIMEDefang or contribute to the MIMEDefang mailing list at the MIMEDefang web site.


As the root of our commercial anti-spam solution, MIMEDefang is one of the best-supported open-source mail filters available. The MIMEDefang web site and mailing list will give you access to community-based support.