What's the best way to test the sending of large volumes of email? I run a newsletter site for a client and as the database has grown to over 40,000 emails I'd like to be able to do test runs of sending that many emails without actually sending that many emails. Also, I've seen some email newsletter/marketing websites that claim to have a verifiable 98% delivery rate. How do they verify that? I think it's done by a third party. Do they run through test mailings by sending to the third party verifier? Finally, what's an average length of time you would expect for sending/delivery of 40,000 plus emails?