Outlook doesn't detect that a mailbox has been migrated to Office 365

We're in the process of migrating our On-Premise Exchange 2013 CU12 to Office 365.
  • Everything is set up.
  • Azure AD Connector is handling the account synchronization
  • It's a hybrid setup.
  • I've migrated a mailbox without errors.
The Mac running Office 365, (Version 16.18) picked up the change in mailserver, prompted for my Office365 login and continued working as before, except it is connecting to Office365.

Now, the PC client, using the same mailbox (it's not a shared mailbox, I'm just running on a PC and a Mac concurrently)  is not so fortunate. The PC is on a Windows domain, the user is logging on to the PDC with DOMAIN\account login.
The Outlook (Outlook for Office 365 MSO (16.0.10827.20118) doesn't pick up the change in mailserver. Instead it connects to the on-premise Exchange Server and says that the mailbox was last updated on Oct 16 2018.

If I run an Autodiscover test from the PC Outlook client, it looks very nice:

<?xml version="1.0" encoding="utf-8"?>
<Autodiscover xmlns="http://schemas.microsoft.com/exchange/autodiscover/responseschema/2006">
  <Response xmlns="http://schemas.microsoft.com/exchange/autodiscover/outlook/responseschema/2006a">
      <DisplayName>My account</DisplayName>
      <LegacyDN>/o=ExchangeLabs/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=37345743bcd0a45d6a18aff6-accountname</LegacyDN>
      <Protocol Type="mapiHttp" Version="1">
          <OWAUrl AuthenticationMethod="LiveIdFba, OAuth">https://outlook.office365.com/owa/</OWAUrl>
          <OWAUrl AuthenticationMethod="Fba">https://outlook.office365.com/owa/contoso.com/</OWAUrl>
        <DisplayName>SharedMailbox1 name</DisplayName>
        <DisplayName>SharedMailbox2 Name</DisplayName>

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So, why doesn't Outlook pick up the changes.

This is a test migration that should reflect any user in our organisation. So, deleting the Outlook account and setting it up again it NOT the solution that I am looking for.

The mailbox in the iPhone (native App), also doesn't pick up the changes, but I'm not entirely sure if this is expected behavior.

Thanks for any input and/or directions.

Have a great day!

Bjorn DirchsenSysAdmAsked:
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Pete LongTechnical ConsultantCommented:
If you create a new outlook profile on the PC does that connect OK?

Ive seen incorrect auto configure.xml files get 'stuck' in peoples profiles before?

Bjorn DirchsenSysAdmAuthor Commented:
Yes. If I set up a new profile, the setup and server connection works fine. Even the shared mailboxes, still remaining on the on-premise server, are accessible.
Adam the 32-bit AardvarkSoftware DeveloperCommented:
If it's the profile-related issue, you can recreate Outlook profiles for all users automatically via GPO. Here is a video tutorial on how to do this:
How to recreate Outlook profiles
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Bjorn DirchsenSysAdmAuthor Commented:
@CodeTwo Software. Nice little video. Good to know.

I do, however, want to keep all the settings, windows sizes etc. etc. that the users has made over time, so re-creating a profile is my last resort - even if it is done automatially via a GPO.
Bjorn DirchsenSysAdmAuthor Commented:
Just thinking - maybe it's because the Outlook client queries the AD and obtain the Exchange server information from the AD, and therefore skips the autodiscovery steps.

Since the non-domain joined mac didn't have these issues, it may be the reason.

Just thinking out loud.
Bjorn DirchsenSysAdmAuthor Commented:
MFA was the culprit...

I had enabled MFA for the account that I migrated to Office 365. That apparently prevent autodiscover from working correctly.

I ran the Microsoft Remote Connectivity Analyzer tool and ran a
That resultet in a serious error:
This line in the errormessage caught my attention:
The Microsoft Connectivity Analyzer is attempting to retrieve an XML Autodiscover response from URL https://autodiscover-s.outlook.com/Autodiscover/Autodiscover.xml for user accountname@contoso.mail.onmicrosoft.com.
<psf:text>AADSTS50076: Due to a configuration change made by your administrator, or because you moved to a new location, you must use multi-factor authentication to access ''.</psf:text>

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I then removed the MFA for the user (account@contoso.com) and Outlook reconnected to the Office 365 mailbox !!!

(and the Outlook connectivity test went trough as well:)

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