ZMailer technical homepage

The ZMailer is a high performance multiprocess UNIX system mailer [ a.k.a. MTA per X.400 parlance ] available free of charge at server

The source-tree is also available thru Anonymous CVS, and Anonymous RSYNC.

Info about the email-list about ZMailer is there.

Some of the documents of the ZMailer have been HTMLized, and are available at following links:

  • Overview of things
  • README about state of the matters
  • README.PERFORMANCE about things affecting on system performance
  • How to do the installation
  • About the smtpserver input policy control facilities
  • CURRENT Work-in-progress of ZMailer Manual (DIR, HTML, PDF)
  • What-there-is ZMailer man-pages
  • If you see weird ORCPT= related errors, you are likely trying to go thru Cisco-PIX firewall.
  • ZMailer feels slow ?
  • Generic story about SMTP relaying misuse, and its control.

  • Year 2000 compability

    See document ZMailer Year 2000 Status.


    The original author of the ZMailer is Rayan Zachariassen (hence the ``Z'' at the name) who was at University of Toronto back in late 1980es, and didn't like the way the sendmail was able to cause serious system loads when doing deliveries, nor the way how it appeared to find a new security hole at the sendmail nearly every week... (That was back n 1980es with sendmail-5.x.)

    The current author, and keeper of ZMailer is Matti Aarnio, who has been doing things of his interests to the ZMailer since 1990, and has been sole keeper of mailer since 1992, when Rayan went to private sector, and disappeared from academic community.

    Matti Aarnio's email address is, and another at