If you are running an email campaign then you probably have some hard choices to make about when to take names off of your list. Of course you are going to remove anyone that requests to be taken off, but how about those other undeliverable names?
Mediapost’s Email Insider has an interesting article called “Losing Subscribers Who Want Your Email”. With all of the Spam and other filtering going on these days it is possible that you are removing people who still want our news. They suggest among other things that you should have several lists of names of people who you remove from your main mailing list. Not all of your precious data should be discarded without making more attempts to find out if it is a bad address, if your email is unwanted, or if there is some other reason that can be remedied.