We have a client that has an email marketing list of about 50k contacts that have at some point opted in to their mailing list. They haven't used the list for a while and on their last campaign got a lot of spam complaints - drawing the wrath of their email campaign provider.

We've been tasked with coming up with a way to help them clean up their list. The plan is to mail each of their customers and ask them to click on a link to confirm their subscription. If they don't click on the link within seven days, we'll remove them from the list. Of course, we'll scrub through the list first to remove addresses that are bad without attempting to email the user (DNS checks, valid email address form, etc). We'll also track which emails bounce and remove them as well. This will be done on a temporary server from one of their lesser used domains.

My question is, how can we send out email to 50k recipients without getting the server blacklisted? The things I have in mind are making sure the domain has DNS setup properly, that the server can be resolved through reverse DNS, has a SPF record, Domain Keys, and valid abuse and postmaster addresses. What else can or should we do?