I'm looking for a company like Cheetah or Epsilon, but one that will be OK with spam-flagging rates a little higher than ideal. We have a sign-up based social network, and a certain percentage of our sign-ups do not confirm their accounts. I need to start sending reminder messages to finish the process. They will have given permission to receive emails, but I expect some spam-flagging because many have forgotten that they signed up and who we are, and many may get multiple messages.

Any recommendation for vendors for this kind of messaging?