All email arriving at Oxford will come either to one of the central mail relays managed by OUCS (Oxford University Computing Services), or directly to a departmental server. Collectively the central relays are known as the Oxmails and route practically all mail traffic into and out of the University.
There are a number of features in the Oxmails to enable basic filtering of a proportion of the viruses and junk mail that users receive. Viruses can be quite destructive and are typically distributed through being attached to emails. Junk mail is the cause of a large number of complaints, both from within and outside the University. It is a great waste of computing resources and staff time, both at the originating and the receiving site.