This “feature” is part of the Simplified Account Creation in Outlook 2016 (and newer), and this lookup occurs before the normal Autodiscover lookup.
Inspecting this traffic, I saw that it was actually giving me my Gmail account information back long before it got to the Autodiscover portion of the lookup – in essence, my Autodiscover records didn’t have a chance to resolve correctly before my account was being pushed to a Gmail login: You can see from my screenshot below that I haven’t even entered the password for my account yet, and it’s already done its lookup and is waiting for me to continue: Sure enough, once I started a network trace through Fiddler I noticed that there was an autodetect step taking place before I would even get to the Autodiscover lookup, and this was going to.
It was actually this forum that gave me an idea on how to start troubleshooting the issue to see if it was affecting me as well.
This behavior can also happen with the Outlook mobile app, as reported on the forums. And yet, when I was configuring Outlook 2016, I kept getting the following popup:Īt first, I thought that maybe it was just an additional popup, and tried to authenticate as normal, but with no success: The oddest part about it is that Autodiscover was configured correctly – even doing an Autodiscover test on would work correctly with no issues. I ran into an issue recently while performing a G Suite to Office 365 migration where my Outlook 2016 clients would begin to Autodiscover as normal, but rather than redirecting to Office 365 as I expected, they would actually present me with a Gmail IMAP login prompt.