So I was contacted by a panicking client. It seemed that all of his Outlook clients could not connect to Office 365 anymore. That meant investigating what was wrong. Upon inquiring he admitted that he changed some DNS settings the day before. But only the SPF record. That didn’t explain connection issues with their Outlook clients. Naturally the first thing I checked where there public DNS settings. There did not seem to be anything out of the ordinary there, apart from a tiny mistake in the SPF record they created. That did not present any insight in what might was causing this problem.
A couple of days earlier we did renew the Exchange certificate on the on premise Hybrid server. But since the auto-discover DNS records where pointing at Office 365 this should not be a problem.
So I turned to my trusty connection testing toolset provided by our friends at Microsoft: https://testconnectivity.microsoft.com/
There on the Office 365 tab I ran the Outlook connectivity test. The following picture is a screenshot of a part of the test outcome. Funny thing that HTTP 503 error for the Office 365 auto-discover service.
A little web research suggested to recreate the federation link with Office 365. I felt that would be a little bit of exaggeration. What else could be responsible for an Office 365 service being unavailable? Needless to say, I tested another tenant. That one seemed to have no problem what so ever. Then it hit me. A quick question to their administrator if anything had changed at the Federation servers of domain controllers confirmed this. Yes, updates where installed, zero reboots given. Great, go reboot those machines….
5 minutes later I got a very happy and relieved sysadmin on the phone confirming that everything was working again. He also informed me they where able to log into on premise servers again. He forgot to mention that fact in an earlier conversation…..*sigh*
If you cannot log into your federated Office 365 environment, check your Domain Controllers and Federation servers. Something might be out of order there.