If you use operating systems which can be influenced by computer virus, then you certainly will welcome antivirus system which filters e-mails, either incoming or outgoing. Yes, it is needed to filter also outgoing e-mails, since there exist viruses which randomly select files on your harddisc, infiltrate them and send to people in you addressbook. There are known incidents where confidential material left the company that way.

There are many products for virus detection. Many of them are suitable to work on the Linux operating system. Fewer of them are those which are suitable to use on the concrete Linux distribution since mnay times they are commercial products distributed in the binary form. But there exist also open source alternatives which quality is comparable to the leaders in the commercial market.