Windows 10 Mail claiming device not compliant with security policy

I ran into a very strange issue. Suddenly two of my machines started to not synchronize my emails from Exchange 2010 server. I noticed it on one machine first but didn't really bother with it since I was using them on my phone. Then my laptop did the same and started crying about not being compliant with the security policy. Weird.

What's even stranger is that I have several accounts on that server. The others were just fine. Nothing the matter. And even stranger, I could open every other folder on the "broken" account than inbox. No problems. Everything's fine.

I spent quite a long time trying to find issues in logs, settings, rebooting machine, checking files for corruptions etc. I readded my account and strangely I got five emails from inbox, even though I still got the complaint about security policy. So maybe it's a content issue?

I moved all emails arrived within the last week from the inbox to a temporary folder. Immediately synchronization worked. No issues with policies. Butterflies and sunshine. Moved emails one by one to inbox. Immediately appeared. Until I got to one email. Then it broke again.

What is the culprit? It's a log check that had a bit too much content. On Outlook Web Access it hangs the browser for ages and cannot really be shown. It's that big. text/plain. iOS Mail app just says "This message cannot be displayed because of the way it is formatted." So it's not just Windows 10 Mail, it's other clients also.

I guess sending huge plaintext emails isn't something that should be done. But surely it shouldn't break the mail client and make it give completely wrong error messages. So this should be fixed.

The message was actually 50MB when I saved it from Outlook 2016. It couldn't show the actual message either. But at least it didn't show random errors.

Reporting it to Microsoft so they can fix it.

Add comment