Hats off to the folks at Fresh Address for bringing to light an extremely important study on the costs & issues of bad email addresses getting into your system. You can find the report on their site here.
Unlike so many irrelevant "studies" that look at things like open rates, this actually shines a light on two giant issues associated with permitting bad addresses into your system:
1) Deliverability. When you mail you are penalized by the ISP's for undeliverable email. Reach a certain threshold and you are blocked. Why would you tie a hand behind your back by trying to mail to addresses that you know are not going to make it?
2) Money. I hadn't really contemplated this one too much, but FreshAddress says that bad addresses cost the retailers in the test an average of $6.7 million dollars annually!
What amazes me is how difficult marketers make Email. I think the problem is that we are so used to marketing being hard, that when we have a tool that makes it so easy to do well.....Marketers must feel like they have to find a way to make it more difficult...