I'll probably end up doing it under Drupal 7 but figure there are more users using the D6 versions.

I trying to figure out what my options are to send out mailing to a rather large list of email address that are not users yet. So from drupal's point of view they would be anon users. The mailings would be infrequent but would probably have over 100-200k(possibly much larger) anon users in the list, plus a growing list of registered users as time goes on. I am thinking of interfacing with campaign monitor to process and track the actual mailing.

What is the largest list anyone has tried handling with EMF and campaign monitor (or other)?
How well did it go?
How long did that first sync take?

Thanks