Outlook connecting to Office365 instead of on-premise Exchange server

GIC-AUA 51 Reputation points
2022-08-15T04:19:16.003+00:00

Hi

We have an on-premise Exchange server. The users are running Office 365 and up to a few days ago, Outlook was working fine and the users were connecting to their local Exchange mailboxes.

Now they are disconnected from their mailboxes and are getting a prompt to enter an account to reconnect to it. However, their domain account never gets accepted.

In the past if we created a new Outlook profile it would automatically find the Exchange mailbox and connect. However, now they get the prompt to enter the account to use autodiscover.xml.

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Before this occurred, we did not change anything on the Exchange server or in the local Windows DNS Manager.

We have tried a number of troubleshooting steps but none have been successful.

We have even added to the registry path "HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover" the DWORD (32-bit)Value with the name ExcludeExplicitO365EndPoint and gave it the value 1.

What could be causing this behaviour?

Regards,

Exchange | Exchange Server | Management
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2 answers

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  1. David Gawler 25 Reputation points
    2024-02-27T09:12:32.15+00:00

    Editing regedit is really bad idea i have found. How about DNS? SSL for autodiscover and fqdn domain name for 2. you need public IP for domain name in question for fqdn.com and SSL autodiscover "A" record for autodiscover.fqdn.com with SSL. fqdn.com should have "A" record of public IP. fqdn should have SSL binded as well in IIS, DNS, exchange ECP.

    1 person found this answer helpful.
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  2. Pasquale Consalvo 5 Reputation points
    2024-08-11T14:18:03.4166667+00:00

    Microsoft has uninstalled the option to connect Outlook Desktop software to on premise Exchange Servers. There is no option to try to connect to Exchange Servers on premise.It's unavailable.

    1 person found this answer helpful.
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