Most smaller datacenters would have no issues with this - It's mostly the larger companies who pull plugs, and then ask questions. If anything, let your potential host see your website/signup process and let them review your spam history reported on newsgroups to have approve your mailings. We've done this with numerous clients who we've put at Nocster and TailorMadeServers with no issues (though TMS is more jumpy regarding spam complaints). I have an opt-in mailing list of over 300,000 (maybe up to 400,000) email addresses hosted at Nocster, and have never even gotten spam complaints regarding it, though I haven't sent out any emails in over a year . We closely monitor spam complaints regarding mailing list clients though, as we've had some clients who've tried to pull quick ones on us.