Prevent Them From Opting Out Of Your Email List

Great advice here from DMNews. Allow users to change their email preferences in addition to opting out of your list. Great advice if you segment you list (as you should, of course.) Allow users to cut down on the frequency of emails, change their topics of interest, or any number of other options. If they still choose to opt out, at least ask a question as to why.

Boost your email list, even during opt out.