For example, if you use the Senate definition to block all advertisements and promotions to your enterprise, you might block unsolicited proposals from new prospects or potential partners. You might block important messages about new conferences or events that could be critical for sales or competitive information. You could block mail about new time or cost-saving products and services that would make a difference to the bottom line for your company.

It quickly becomes clear that each organization must not only identify which messages are spam, but also must make sure that messages that are needed by one department or another are not identified as spam. It sounds easy, but it is not.

Many people think that there must be some rule that would knock out the majority of spam. For example, an initial reaction might be to create a rule that defines spam as any message that contains one of George Carlin's "Seven Words You Can Never Say on TV." If you don't know what they are, find his 1972 comedy album named "Class Clown." It is very funny, assuming you don't take offense as he names the words.

However, somebody in customer service will quickly object because complaints could contain one or more of those words. Good customer service departments will not want a single complaint blocked. There is always an exception to black and white rules. [One of our readers works in the IT department of a hospital and reports there are some words often found in spam that they absolutely can't block in the hospital -- for obvious reasons. -- Ed.]

What about spam filters that use community voting to decide whether a message is spam? Many of these systems are popular with consumers. Unfortunately, majority rule does not always protect the email rights of the minority. For example, a group of people outside of your company might decide an offer to sell medications by email is clearly spam. But the message would be very relevant for companies in the pharmacy business -- either because they want to obtain cheap medications or want to know what the competition is doing. For them, such a message would not be spam.

It comes up again and again. The definition of "not spam" seems to be as important as the definition of "is spam." A simple definition of not spam may be that a "relevant message" must get through, no matter it says. Unfortunately, it is hard to know whether a message will be relevant to somebody else. The definition of "not spam" will vary company by company and may vary department by department.

Therefore, before selecting a spam filter, it is important to make sure that it will identify "not spam" for your company -- even if the message otherwise looks like spam.

How to develop a spam-base for your organization
One way to do this is to collect a corpus of spam and then find relevant messages. A quick process is to identify spam using a spam filter, such as the one built into Microsoft Outlook 2003. Add to it messages that selected members of your organization would think are spam. Ask them to move such messages into an Outlook folder named "spam" or "junk e-mail." After a week or two, you may have a very good collection of spam messages in various mail folders ready for collection.