Just my opinion here, however, it may be best to let dead dogs lie,
especially if it has been dormant for a while. If you continue to offer
informational and helpful emails and the response is still null, perhaps
send one final email (or even a few "final notice" type mailings) that
ask them to subscribe to one of your more active lists.
It may be that you burned some bridges that are just not repairable,
and again, if that's the case, perhaps letting dead dogs lie would be
the best route to take.
If your open rates are still low, you will need to work on creating some
compelling subject lines to grab their attention. If open rates are proving
to be ok, then, you obviously need to work on writing more compelling
content. Try promoting a little more inter-activeness with your subscribers.
Ask open ended questions at the end of each email asking them to post
their thoughts on your forum, blog, message board or even by hitting the
"reply" button. At least you will know that those who end up responding
in some way are still interested, at which point, try to get them on one
of your other, more successful lists, and simply let the dead list die out
completely.
This is actually a pretty good question Crystal, thanks for your post. I
can't wait to see what others will have to add as well.