Outlook connecting to Office365 instead of on-premise Exchange server

GIC-AUA 11

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.

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,

Aholic Liang-MSFT 13,741 Reputation points Microsoft Vendor

2022-08-16T06:29:45.927+00:00
Hi @GIC-AUA ,
I want to know if you create a new profile with only one on-premises mailbox, will this issue persist?
If yes, please use ExRCA to check if it can connect to Exchange server successfully.

If Autodiscover is working and pointing to the correct server, You should be able to stop Outlook from checking Office 365 settings by setting both registry keys.

HKEY_CURRENT_USER\SOFTWARE\Microsoft\office\16.0\outlook\autodiscover DWORD: ExcludeExplicitO365Endpoint Value = 1 HKEY_CURRENT_USER\SOFTWARE\Policies\Microsoft\office\16.0\outlook\autodiscover DWORD: ExcludeExplicitO365Endpoint Value = 1

Please restart the Outlook2016 client after you modify the registry and recreate the profile to see if it can works.
Aholic Liang-MSFT 13,741 Reputation points Microsoft Vendor

2022-08-23T08:43:58.367+00:00

Hi @GIC-AUA ,
Thanks for your detailed information.
Do you have any websites running with the root domain(domain.com)?
If so , the website will take over the request of search for the Autodiscover URL.
Please following steps below to add the value ExcludeHttpsRootDomain will force Outlook to skip domain.com and go direct to Autodiscover.domain.com, and then see if it works:

1.open regedit.exe on the client computer and locate
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover
2.add a DWORD value named ExcludeHttpsRootDomain and set its value data to 1
3.restart Outlook and check if you are able to configure the profile

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Aholic Liang-MSFT 13,741 Reputation points Microsoft Vendor

2022-08-30T08:38:46.2+00:00

Hi @GIC-AUA ,
It has been a few days and I am checking in to see how things are going on with this issue.
Does this issue have any updates?
David Gawler 5 Reputation points

2024-01-22T01:37:20.63+00:00

Exchange is a rhino on heat. I get a problem where i can connect only on my local LAN IP connectivity. soon as i switch my IP to my public IP address of my router it does not connect and tries to connect to office 365 online, clearly it is a DNS issue of some sought, mail flow, autodiscover works fine on my mobile and iphone even mac clients. when it comes to windows 10, 11, it just does not connect from a public IP and tries to connect to microsoft 365 online exchange, it needs to default to microsoft exchange on premise, regardless of LAN or WAN IP address. Any ideas?

9 answers

GIC-AUA 11 Reputation points

2022-08-19T13:48:04.127+00:00

Hello Aholic Liang-MSFT

Thanks for your assistance.

All mailboxes are on-premises and we are not able to create new profiles because it seems as if there i a problem with the autodiscover.

I tried the ExRCA and it does not connect to the Exchange server using autodicover.

I tried setting both registry keys and it made no difference.

Regards,
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Aholic Liang-MSFT 13,741 Reputation points Microsoft Vendor

2022-08-22T09:06:26.083+00:00

Hi,

I tried the ExRCA and it does not connect to the Exchange server using autodicover.

If possible, please provide a complete screenshot about it for our better research. (In order to avoid the disclosure of your privacy, please remember to hide your personal information).
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GIC-AUA 11 Reputation points

2022-08-22T19:33:24.98+00:00

Hi AholicLiang-MSFT

When I run the Microsoft Remote Connectivity Analyzer, I enter the information as follows:

The results are as follows:

I notice in the results, the host is returned as domain.com but I think it should be <mail_server_computer_name>.domain_name.local.

On the internal network Outlook Web App works with domain.local but not domain.com and we need to specify the computer name of the mail server.

I hope the information provided sheds some light on what could be causing the problem.

Regards,
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GIC-AUA 11 Reputation points

2022-08-23T12:18:48.377+00:00

Hi AholicLiang-MSFT

Yes. There is an external website hosted with domain.com.

On the client computer, I added the DWORD ExcludeHttpsRootDomain and set its value to 1.

When I try to create the Outlook profile, I get the following pop-up:

In the server field it has the external domain and in the username it the the email address.

I restarted the client computer just to see if it was necessary after changing the registry, but it made no difference.

Regards,
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Aholic Liang-MSFT 13,741 Reputation points Microsoft Vendor

2022-08-24T08:56:54.853+00:00

Hi,
Please have a check that the Autodiscover CNAME record is set up in DNS to point to the mail.contoso.com.
Autodiscover service in Exchange Server | Microsoft Learn

According to Autodiscover process , add the value ExcludeHttpsRootDomain will force Outlook to skip domain.com and go direct to Autodiscover.domain.com .However , you won't receive any useful information from “autodiscover.domain.com/autodiscover/autodiscover.xml” if you do not set Autodiscover record in DNS.

GIC-AUA 11 Reputation points

2022-08-24T12:57:36.907+00:00

Hi AholicLiang-MSFT

I reviewed the link to the document you sent Autodiscover service in Exchange Server | Microsoft Learn (https://learn.microsoft.com/en-us/Exchange/architecture/client-access/autodiscover?view=exchserver-2019#autodiscover-in-dns).

It is a bit confusing because there is a section that states the following:

*

> Autodiscover is simple to set up for your domain because it only requires that you create a CNAME resource record in your external (public) DNS. CNAME records let you hide the implementation details of your network from the clients that connect to it. Used internally in your network, CNAME records allow users to use the simpler URI mail.domain.com instead of host.examplemachinename.domain.com.

*

It asks us to create a CNAME record in our external (public) DNS but the problem we have is that the Outlook has connectivity issues with the local Exchange server so why would it need to contact the external DNS and not the local DNS.

In our local DNS we have an A record for the Exchange server as follows:

We have a CNAME record as follows:

I'm really confused as to why I need to worry abut the public DNS. The local domain is domain.local. When the A and CNAME records were created, it automatically used domain.local and not the domain.com external domain.

Regards,

Aholic Liang-MSFT 13,741 Reputation points Microsoft Vendor

2022-08-26T09:24:18.69+00:00

Hi,
I think the main reason for the issue is that your email address doesn't correspond to the FQDN of Autodiscover.
Please change the FQDN of Autodiscover like Autodiscover.domain.com to see if it changes.

GIC-AUA 11 Reputation points

2022-08-31T01:50:24.357+00:00

Hi AholicLiang-MSFT

I'm not able to change the FQDN of autodiscover because it is greyed out. I'm only able to change the FQDN for the target host, It can be changed to <computer_name_of_exchange_server>.domain.com but iy makes no difference.

Regards,

Aholic Liang-MSFT 13,741 Reputation points Microsoft Vendor

2022-09-02T09:46:06.91+00:00

Hi,
I am sorry to come back late. Could you please re-confirm the following questions:

Are the users with issue connected to the Exchange server from internal or external?

Whether the computers they are using are domain-joined?

Please refer to the following link to use Test-Email AutoConfiguration feature of Outlook and post a screenshot of the results that under the "Log" tag .
https://answers.microsoft.com/en-us/msoffice/forum/all/mailboxes-test-e-mail-autoconfiguration/19f9c90a-4640-46c4-a574-dbec29bdb8ba

(Notes: Please only select “Use Autodiscover” , and don’t forget to hide your personal information! )

Aholic Liang-MSFT 13,741 Reputation points Microsoft Vendor

2022-09-07T02:58:54.497+00:00

Hi,
Just checking in to follow up with this thread. If you have any questions or need further help on this issue, please feel free to post back.

GIC-AUA 11 Reputation points

2022-09-15T20:34:58.28+00:00

Part 1 of 2

Hi

I'm still having issues and now it is much worse.

I cannot create an Outlook profile for new users to access their Exchange mailbox in the internal network. At the
moment they can only use OWA to connect to the on-premises Exchange server.

Existing uses keep getting a pop-up to authenticate on the Exchange server and if they enter the credentials the message disappears and then re-appear seconds later As you can see in the image below, Outlook states "Connected to: Microsoft Exchange".

GIC-AUA 11 Reputation points

2022-09-15T20:36:45.71+00:00

Part 2 of 2

The issue I have is for only for users on the LAN with the on-premises Exchange server.

We tried the the "Test-Email AutoConfiguration" tool in Outlook and got the results below:

The on-premises exchange server is xxx-v-svr-02.domain.local but in the tool it shows xxx-v-svr-02.domain.com.
On the last line it has https://domain.com/autodiscover/autodiscover.xml Succeeded. However when we ping domain.com it is pointing to the external mail server.

The setup has always been as follows: On-premises Exchange forwards emails though a Smart Host on the external hosting company (domain.com). A utility on the Exchange server uses POP3 to retrieve the emails from the mailboxes on the external email server at the hosting company and forwards them to the corresponding Exchange mailboxes. This worked fine for years but something change recently.

Somehow the autodiscover on the local network is ignoring the on-premises Exchange server and going out to the External hosting company.

Regards,
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GIC-AUA 11 Reputation points

2022-09-23T18:02:21.503+00:00

Hi

I'm still having issues. Did you see my last post?

Regards,
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Stuart Elliott 106 Reputation points

2022-11-14T11:25:39.57+00:00

Did you ever solve this, I get this from time to time, also with a .local domain (although I do have a mydomain.co.uk entry in the local DNS server for the internal ip-address to try to stop it going out into the big bad world.

I am just starting the process of migrating to Office365 in the cloud, and I fear all the hacks and slashing I've done over the last 15 years or so to registries and AD policies are going to make for a real bad time though :(
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Phil Wize 0 Reputation points

2023-10-18T14:21:17.56+00:00

Are there any news related to the problem?
I have the exact same setup and therefore the same problem.
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Jonathan Obenauer 0 Reputation points

2023-10-20T16:59:27.7433333+00:00

I also started having this exact issue on 10/18/2023
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