Making sure you are not considered spam
I just received an e-flyer from Bell which hotmail windows live mail marked as a potential phishing spam. This triggered the memory of when I was at Points and testing a new product for American Airlines. At the end of the process, a confirmation email was sent to the users, but it would get flagged by AOL as spam and eventually would get put into the blacklist.
So here is another thing that you need to check on when wearing your QA hat (which is a bigger hat than the Tester one): Make sure that your organization has contacted the major email providers and make sure that your sending addresses are in their whitelist of that they conform to the mail standards in such a way as to not trigger their filters.
The postmaster site provides an overview of the services businesses can make use of when interacting with windows live mail. Specifically, have a look at the Safe list Information and Sender Solutions sections. I’m willing to bet all the other big mail providers offer similar resources as well.