I have come across a weird issue that I can't seem to find to much on. The issue is exchange accounts on iOS using the Outlook application occasionally come up as "blocked" to the user, sometimes removing and re-adding the user works but eventually the only fix I have found is resetting IIS which obviously disconnects everyone causing our Service Desk an over run of tickets coming in.
Not sure if it's related but... we also had an issue whereby emails would stop going to mobile devices and resetting IIS fixed that to but that's come back 2-3 times since it started happening so It does make me think this is IIS related.
Has anyone come across this before? If so is there any better way of solving this than what i'm currently doing?
Bit of background
Running exchange server 2016 connected to an on-premise active directory
Issue mainly effects iOS users but has been known to crop up on andriod users from time to time
The linked issue happens on all client apps but not on our OWA external access