I've found when doing mass mailings the best solution is to use a service whose sole job is to insure your email gets delivered. I haven't used many such services, but Constant Contact (constantcontact.com) comes to mind. They provide things like tracking how many people viewed the email (by using HTML in the email to load a remote image, I believe), tracking link clicks inside the email, etc, though for your purposes it doesn't sound like this kind of service would be helpful.

In this world of spam paranoia, I've found it to be way too much trouble to do mass mailings yourself and expect to actually get around all the spam filters. Services like Constant Contact are paid to do just that, so your chances are much better.

I use AuthSMTP for all of my personal and business outgoing email and it's great (I've been using them for almost two years now). I've never had any downtime and they have a simple interface to view sent emails, so I can easily confirm an email was actually sent if I'm in doubt. The one or two times I've interfaced with their support, they seemed technically adept and were very helpful.

For my clients who insist on writing scripts to do their own mass mailings, I always recommend using AuthSMTP and simply writing the script to stay within AuthSMTP's stated volume guidelines (maximum of 50 recipients per single message, though they recommend keeping it to 10). Oh, and they do have a "Show Errors Logged" section that shows you all the emails that didn't go through.