Rather than spending money for an outdated Microsoft server implying a lot of configuration, setting, and microsoft specific bugs, I'd rather suggest you to subscribe to one of the LimeSurvey Hosting solution:
www.limesurvey.org/2015-09-02-06-51-08/hosting
They work out of the box, include the mailing system.
Concerning the problem itself, it's hard to answer knowing that a lot of people are using Microsoft servers with LimeSurvey without any problem. If it was a bug in LimeSurvey, we'd probably have many complaints about it. It's not the case. So, IMHO, it's probably a configuration problem in global settings. Have a deep look in global settings.
Also, a solution more and more promoted by microsoft itself, is to use a Linux Virtual Machine on your Microsoft Server:
techcrunch.com/2016/11/16/microsoft-joins-the-linux-foundation/
msdn.microsoft.com/en-us/commandline/wsl/install_guide