Information Systems & Services (ISS) - postfix

Information Systems & Services (ISS)


Postfix is the MTA on our mail gateways. It is an alternative to the widely used sendmail program. It attempts to be fast, easy to administer, and secure, while at the same time being sendmail compatible enough to not upset existing users.

Anti UCE Measures

We have based our postfix config on Jim Seymour's anti-UCE cheat sheet. This has proved very effective. We are currently blocking in excess of 1,000 messages per hour. Here is a typical summary of our mail log.

Rejected Mail

Occasionally genuine mail to DCU accounts may be blocked. This information page explains the different reject messages.

As you can see from our mail log summary we mainly reject mail based on

  • Header
  • DNS Blacklists
  • Helo Commands
  • Sender Address


This is primarily an anti-virus measure which blocks dangerous mail attachments. Increasingly viruses propagate by spam and often attack anti-spam sites/organisations. This page explains which attachments are blocked and how to mail such files to DCU mail accounts.

DNS Blacklists

Blacklists are explained