2. And now some braces: a personal layer of defence
Of course many users on the University network access email accounts outside the University network and this can provide another route for a virus to infect your computer. Many university members regularly use third party provided email accounts such as Hotmail, Yahoo!, GMail etc. from their computer and once a virus infected email is opened, regardless of where it is stored, then your computer can be infected.
To provide further protection from viruses OUCS distributes and supports Sophos anti-virus software, and this software is available freely to all University members. Sophos runs on a variety of platforms and instructions on installing and using it are available for Windows, Mac OS X, and Linux machines.
To compund matters it's not just email that provides a way for your machine to be infected with a virus. It is becoming increasingly common for viruses to be propagated via USB drives, by visiting compromised web pages, by downloading files that have been crafted to take advantage of security vulnerabilities, and, of course, by simply using an unpatched system.
It is often said that users of non-Windows machines don't need to worry about viruses; this is foolhardy! As always with security a belt and braces approach works best, don't rely on obscurity, install Sophos and be safer.