We connect to several 365 emails via pop3 every few minutes throughout the day. This worked well for some time, but we have had more and more connection errors when trying to connect to outlook.office365.com and can sometimes not get connected to it for hours and hours. We think we are being throttled, but don't know the criteria/limits that are being used by MS. We typically receive around a 1,000 emails between 6-8 email addresses per day. Has anyone else experienced this? Is there a way around this or something we can do to improve the reliability of this connection?
Microsoft doesn't post any throttling information, you will have to contact support and work with them on this. That said, there isn't any "number of received messages" type of throttling that I'm aware of, it's more likely something like a number of sessions, etc.