Outlook 2016 Autodiscover Fails on Hosted Exchange Mailbox when Microsoft Account Present

It's been a few months since I had any fresh moans about Microsoft. Yes Windows 10 is still an awful (unfinished) operating system but that is an old but ongoing moan. I do have a brand new issue which has cost me probably the best part of three days of my life I will never get back – and it’s all down to the ineptitude at Microsoft.

Over the past few months we’ve had an issue at one site on a Windows 10 based PC running Outlook 2016 where Outlook just could not be configured with an externally hosted Exchange mailbox. No matter how many different ways we attempted to configure this user’s account we just could not get it working.

We have still not deployed that many systems with Windows 10 (we’re leaving it as long as possible) and so it’s an easy target to blame. After various diagnostics and tests one of the tasks we finally undertook to try and resolve this issue was a full wipe and reinstall of Windows 10 and Office 2016. I was convinced Windows was borked and a reinstall should sort it. It didn’t.

I was surprised than that even after this back to basics rebuild the mailbox would simply not be properly detected via Autodiscover – which is a huge problem since the complete tools at Microsoft have removed the ability to manually configure an Exchange mailbox in Outlook 2016 or later.

So, I moved on to figuring out why Autodiscover wasn’t working. Let’s be clear - the record is configured correctly. The mailbox would setup okay using different versions of Outlook from the same site and even from different sites. I did lots of research and concluded that I needed to setup DNS differently… but this didn’t make sense either. You get a hunch for these things after a while.

Finally – I figured it out. Every time I went to setup the mailbox using the OL2016 setup routine, credential manager would have entries for ‘office365.com’. Given the mailbox in question is NOT hosted by Microsoft I felt that there must be a change in the way Outlook 2016 was treating Autodiscover. Outlook kept thinking this mailbox is hosted at Microsoft… but why?

It turns out that because this individual has a Microsoft Account with the same email address (for Skype – NOT for email) that Outlook was IGNORING the Autodiscover record as configured and trying to set the mailbox up as if it was hosted at Microsoft.

My simple fix was to add a different  email address to the Hosted Exchange mailbox (setting the old one as an alias of course) and – hey presto – the mailbox setup worked first time.

The basic issue is that – if you have a Microsoft account for Skype that uses the same email address as a hosted Exchange Mailbox (and you are using Outlook 2016) then you are very likely to have the same issues. This may be limited to the Professional Plus version.

Another waste of time sponsored by the cretins at Microsoft.

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