Do you track your opt-in data?
"Surprisingly, I'm finding that many marketing managers aren't tracking this. This is sad, because sometimes this data is the last line of defense against you getting sanctioned over allegations of sending spam. When an ISP, ESP, or recipient asks for proof that a recipient opted-in to your email, they're asking for those exact details."

Four odd email ideas that (maybe) make sense
Mark Brownlow shares four email marketing concepts that seem wrong but might be right.

Three more odd email ideas that (maybe) make sense
And the list continues: poor open rates are a good thing, good responses don't indicate success, and delivering value is a bad idea.

You Need to Have a Privacy Policy 
When I reach out to ISP’s to resolve delivery issues, one of the items they almost always require is that email marketers have a clear and detailed privacy policy.

Let Your Subscribers Tell if the Email is Relevant 
Don't know if your subscribers find your emails relevant? Just ask them!

Link Tracking - Profiles Drive Greater E-mail Relevance
Stefan Pollard "The following two tactics will help you collect data at different points in the customer or subscriber relationship. There are more, of course, but these two work for me time and time again."