Cleaning Up Large Mailing Lists: Removing Bad Addresses

Jeff Bennett

Supporting corporate Web sites, especially retail ones, often includes administering mail servers that perform regular mailings to large customer mailing lists. Managers are generally motivated to increase the size of these lists by any means necessary, as this is a good way to increase the customer base. In theory, the more email addresses you mail to, the more customers you have. In practice, this often means "encouraging" the people who visit your Web site to register before they can continue onto more desirable site functions -- a practice not well loved by all end users.

The Problem

While the marketing department of any firm may be pleased to have accumulated a mailing list of 500,000 email addresses for their weekly mailing, this joy is not always shared by the systems administrator. Besides the minor burden of efficiently managing a huge send every week, the main headache is the fact that many of the addresses collected will be bogus. When an annoyed Web surfer inputs "bobsyeruncle@nodomain.all" as his email address in the registration process, the effect of one bad address added to the mailing list is less than minimal. But what if 10,000 people do that each week?

There's is no limit to the imagination that goes into creating bogus email addresses; however, the amusement wears off quickly when they start clogging up your system. Besides lengthening the duration of your sends, the bounces come back by the thousands, and the stern emails start to arrive from other postmasters, both automated and human, informing you that rules are being broken. Even if you are emailing only to solicited customers, you may find yourself on spam lists and blacklists if you are sending thousands of phantom messages that do nothing more than take up bandwidth and machine resources as they are processed and passed back and forth.