If your users have used their e-mail address on a publicly available Web site such as eBay recently, you may have noticed that the amount of spam you're getting in to your mail server has dramatically increased. Currently, spam represents between 50% and 65% of the e-mail I receive, and that's not counting things like Tips or e-mail newsletters in the spam category. The explanation for this is pretty simple; the large bulk mailers have figured out how to troll a site for Internet addresses, in the same way that the search engines troll sites for keywords to index. It's simple, just search for <string>@<string> and you've found a valid address to try.
If the spammers want an efficient mailing they purge any address that is returned repeatedly, but most spammers don't do this, because it takes too much time. Since spammers get paid by the number of addresses, there's also no incentive for them to prune their lists. There aren't as many spammers as you might think, but you would be amazed (and saddened) at how much of the Internet's traffic is spam-related.
So there are some important caveats for users that you should tell them about, in an effort to reduce the amount of useless e-mail traffic you're going to get.
First, if users must use an e-mail address in a public Web site, urge them to use a secondary address, or a site specific-address if possible. Doing this will actually give you a very simple filter option based on any traffic to that e-mail address.
You can also invest in spam filters, and there have been a spate of recent reviews on this type of software. Some spam filters are quite good at removing bulk-generated mailing.
There are some other things users can do, because it is almost unavoidable that some of their e-mail addresses will get put on a mailer's list. First and foremost, no user should EVER respond to spam. A response confirms that the e-mail address is an active one, and invites more spam.
If a spammer offers a mechanism for removing recipients from a list, your users should not exercise it for the same reason. And many spammers now are able to disguise the true origin and identity of their mail. In one technique, called "munging," the address gets a special character like an X added, so that the address firstname.lastname@example.org would become nameX@domain.ext. The X helps defeat programs that scan for addresses.
Eventually spamming will be illegal or controlled and made more difficult by features in operating systems. But until then, keep in mind these precautions for a safer e-mail experience.
Barrie Sosinsky is president of consulting company Sosinsky and Associates (Medfield MA). He has written extensively on a variety of computer topics. His company specializes in custom software (database and Web related), training and technical documentation.