Information Services

Introduction to the mail relays

This explains what the mail relay service does and how it handles spam and viruses in mail messages.

Mail relaying services provide the underlying infrastructure to support the safe delivery of email into and out of the university.

We provide two sets of mail relays. The first is internally facing and routes email between the different email services inside the university. These relays will also add the university's charity status message to any message that does not already contain one.

The other set of relays allows the routing of email from outside the university to internal mail services. These relays protect the university from unwanted spam, viruses and other malware.

Virus checking

All mail is scanned on the relays for viruses using two virus detection systems. The first is a commercial package called Sophos. The second is a free community supported package called ClamAV. This two level system ensures a higher degree of protection than one alone and this complements the use of Kaspersky on user's desktops providing a third level of protection.

Spam handling

The mail relays also protect the university's mail services from spam. This is done in two ways:

  • Block lists are used to automatically reject any mail from known spammer sites or from IP address ranges nominated by ISPs that should not be generating email. This blocks up to 97% of all incoming spam.
  • SpamAssassin is used to scan the remaining mail to determine the likelihood of a message being spam. A score is inserted into the mail header before passing the mail on. Any message scoring more than 10 is returned to the sender and not passed on. User's can then filter the remaining mail using this score with a score higher than 3 or 4 being likely spam.

Maximum message size

The maximum message size supported on our mail infrasructure is 25MB. This is a limit that is set to match our out-sourced email and diary service provider and cannot be altered.