I think, in this case, it's best to set up in your exchange server an e-mail group address so that you can send to the group. SendMail is a rather limited method, as you noted, in that it can only send to one person at a time.
Robert Martin [Hall of Fame] Please consider giving a Kudo if I write good stuff ----
Why automate? I do automated testing because there's only so much a human being can do and remain healthy. Sleep is a requirement. So, while people sleep, automation that I create does what I've described above in order to make sure that nothing gets past the final defense of the testing group. I love good food, good books, good friends, and good fun.