Most attacks performed by Microsoft are SMTP attacks; pic related describe it.
What can they possibly achieve with that ? It's mostly used to get valid emails in order to spam them. However, I recall seeing a documentary about Cyber Security experts who used that kind of attack as a test, they sent a spam linking to a porn page they made to all employees in order to store credentials and stuff like that.
Sorry if I'm not very precise, it was long ago and english isn't my mother tongue