As Donatello says, I'd rather not encourage bulk mailing, but I just don't understand the question. If you have the facility to bulk mail, how come you can't test mail? It's the same process, only using a small test database instead of a live one, and viewed in a range of mail clients.
maybe bulk email is not the correct word ( i thought was a synonymous for newsletter ), i'm not a spammer :-) i have a PHP tool that send email to people that volunteering submit to information newsletter
i actually code with tables, etc but to test the results i spend a lot of time side a need to open different email client on different operating systems, and sometime what fix the problem on windows mail cause a different one on a different email, client
i don't have outlook, i don't use it
i found a very cool service, not sure if i can mention it, but it as a loto a features
the problem is that they don't have a pay per use plan but only a 79$ monthly subscription, that i is way too expensive for me