Exchange Online protocol authentication policies control what protocols a user can connect to mailboxes with, but it would be much better if we didn’t have to worry about some old and insecure protocols. Azure Active Directory gives Office 365 tenants the chance to clamp down on IMAP4 and POP3 connections and close off some of the holes that attackers try to exploit. Microsoft says that this can lead to a 67% reduction in account compromises, so that’s a good thing.
An outage in a U.S. datacenter on September 4 caused problems for Azure Active Directory with a ripple effect on Office 365. It’s a good example of how cloud services depend on each other, so when one fails, another has problems.
If you’re responsible for running the local network used by an Office 365 tenant to connect to Microsoft’s network, you need to know about the IP addresses and ranges used for Office 365 endpoints.
People sometimes complain about Office 365 network performance. The root cause is unlikely to be in Microsoft’s network. It is much more likely to be in the “last mile” to the user device.