Depending on how long you've been gathering names, your list probably contains at minimum 10% bad addresses, and that number could be as high as 40-50%. Much of this is due to the fact that every year approximately 32% of Americans change their email address. Matt Blumberg, Founder & CEO of Return Path, an email change of address system, says, "About a third of everyone's list of going to decay every year. People have been acquiring opt-ins at such a rapid rate that the problem's been masked. There's never been a focus on retention before; but it's starting to come out now."

According to Blumberg, "The average consumer is on 10-12 lists, but when people change their address, they generally go back to only a handful of sites to update them. They'll get weather and stock quotes and forget about everybody else." Privacy issues complicate email change of address. Marketers and online publishers must obtain a brand new permission to start emailing someone at their new address.

Currently there are three main contenders in the email change of address business, all of whom obey privacy regulations. Each has its pluses and minuses. Return Path plans to offer change of address services to consumers through dozens of allied sites and vendors. Veripost gets thousands of consumers to register their changes at its destination site. ActiveNames offers consumers a free plug-in they can download to inform lists about email changes. Given the amount of money companies spent in 2000 collecting opt-ins, we'll bet all of these services will get plenty of business in 2001 as marketers rush to protect their investment.

How much is it worth to you to get that new address? Consider how much that name cost you to acquire in the first place, and how much it was worth. Generally "revived" customers are worth more than new ones because they've proven their interest two times around. Plus, if you're in a particularly finite marketplace, those revived customers may be critical to your success.

BTW: Are you depending on a call center to gather emails for you? According to Blumberg, the two most typical call center email entry errors are: spelling out "America Online" instead of typing "aol.com", and typing "at" instead of "@". Considering the fact that call centers often charge $1 per email address collected to cover extra phone time and data entry, you might want to raise your ROI by routinely sending all operators a little educational note.