MAPI Outlook Microsoft login request
Question asked by echoDreamz - 7/14/2020 at 4:16 PM
I've seen it a few times and we've had a few customers ask about it. MAPI works fine, but randomly there is a Microsoft login prompt that Outlook shows asking for credentials. It's not just a normal Outlook login prompt, it's a Microsoft account login window.

Restarting Outlook makes it go away, but it comes back randomly, sometimes hours, sometimes days, sometimes weeks later.

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Dennis A. Replied
I'm seeing the exact same issue and have an open ticket with SmarterTools about this.

What seems to fix the issue for me is to create a registry entry at Computer\HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\AutoDiscover (Office 2016 and later). Make a DWORD entry with name ExcludeExplicitO365Endpoint and value 1. This prevents Outlook from contacting Office 365 directly and instead will use autodiscover. I'm not seeing the login prompts anymore now, and my 2nd account in Outlook (which is an O365 mailbox) also works without problems.

James Ratliff Replied
Wanted to bump this as we have a user who is experiencing this issue and while I don't mind editing my own registry we've recently upgraded and only have a few users on MAPI with Outlook and adding registry entires for every user is not an optimal or efficient solution.
Larry Duran Replied
Employee Post Marked As Answer
Unfortunately Microsoft makes external requests to their O365 servers that we cannot control.  We've opened up tickets with them on how to fix the issues when trying to connect with on prem servers, like SmarterMail, and registry changes are the only workarounds they have provided.
Larry Duran
Software Developer
SmarterTools Inc.
(877) 357-6278

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