Scam, otherwise known as Nigerian 419 (in reference to Nigeria’s 419 law prohibiting this type of practice), and Phishing are also a form of spam and should be interpreted as such by anti-spam solutions.
In practical terms, a Scam usually takes the form of a letter in which someone tells you that they have a large sum of money and that they need to use your account to transfer this money quickly, in exchange for which they offer you a percentage of the said sum. If the victim accepts, he or she will have to advance a large number of costs (notaries, security companies) before the transfer is effective. The transfer will obviously never take place.
Phishing is a so-called “social engineering” technique designed to rob individuals of their login details, passwords or credit card numbers…
Spam and virus propagation techniques are very similar. So are the spammer and virus designer communities. For example, the simple fact of using an anti-spam software blocks almost 85% of email-borne viruses.
I do think, however, that an e-mail protection solution should, in addition to antispam, incorporate one, or preferably several, antivirus programs to block all viruses.