Do you think that double opt in is really important? I find it a real PITA as some people I target are very dumb. Smart enough to open an email and see a news letter, but many times don't really understand they should click that link on the email in order to receive the newsletters, they don't even pay attention to that email!If your complaints are to high, then I recon you should sort that out rather than going to another EMS otherwise the problem will follow you. Do you use a double opt in system with your clients?