@greg_york
Yes, Microsoft will do that when it see's too much outbound "spam-like" emails going out. Microsoft's platforms aren't intended for mass emailing. You can subscribe to 3rd party providers for that kind of service.
If your email is in O365 Business, then contact your admin to get it unblocked. If this is a personal account follow the instructions in any email you received that told you that you were blocked.
