Not able to add O365 mailbox in Outlook

Question

Hello Team,

I have recently migrated mailboxes from Exchange 2016 to O365 and it was successful. I have also updated all 365 DNS records such as MX, CNAME, TXT and all of them are well propagated. I am able to use mailboxes through Web Mail successfully.

Now, the issue is I am not able to setup outlook for Microsoft 365 mailboxes as it always prompting for password window and I am using the same password which I am able to login web mail.

As these mailboxes were migrated from Exchange 2016 to O365 hence they were all using outlook with Exchange 2016 services on every computer. I have uninstall the Microsoft suite from many computers and have downloaded from office.com which is new M365 suite and get them installed and when I tried login with email address and password it is again prompting for password window.

I have then installed SARA tool and upon checking it is showing no error, everything is showing green and all good. At the last it is asking to setup outlook profile when I am trying to add then again getting same error like password window popping up again and again.

Computers are different domain joined but I believe O365 does not have this dependency because it mostly require Autodiscover and that is added successfully in DNS records.

I have tried setting up same mailboxes on different machines outside of the domain and I am able to setup successfully, only the issue with there computers.

I would request for some help on this please!

Thanks,

Answer 1

Hello,

I understand that you are facing an issue with setting up Outlook for Microsoft 365 mailboxes after successfully migrating them from Exchange 2016 to Office 365. The Outlook client keeps prompting for a password, even though you are using the correct password that works for webmail access. It seems to be specific to computers within your domain.

Here are a few suggestions to troubleshoot and resolve the issue:

Check Credential Manager: On the computers where you are experiencing the password prompt issue, check the Windows Credential Manager to ensure there are no outdated or incorrect credentials saved for the Exchange server. Remove any credentials related to the old Exchange server to ensure that Outlook uses the correct credentials for Office 365.

Clear Cached Credentials: If there are cached credentials causing the password prompt issue, you can try clearing the cached credentials. Follow these steps:

• Close Outlook and any other Office applications.
• Open the Control Panel on the affected computers and go to "User Accounts" or "Credential Manager."
• Look for any credentials related to the old Exchange server or Office 365. Remove them.
• Restart the computer and try setting up Outlook again.

Test Autodiscover: Ensure that Autodiscover is functioning correctly for the affected computers. You can use the Microsoft Remote Connectivity Analyzer (https://testconnectivity.microsoft.com/) to test Autodiscover and check if any errors or misconfigurations are detected.

DNS Resolution: Double-check that the DNS settings on the affected computers are correctly configured to point to the Office 365 environment. Make sure that the computers can resolve the Autodiscover records and other Office 365-related DNS records.

Disable Proxy Settings: If your organization uses a proxy server, try temporarily disabling the proxy settings on the affected computers and then attempt to set up Outlook again. Proxy settings can sometimes interfere with Autodiscover and cause password prompt issues.

Firewall or Antivirus Software: Check if any firewall or antivirus software on the affected computers is blocking or interfering with the connection between Outlook and Office 365. Temporarily disabling or configuring the software appropriately can help troubleshoot this.

If the issue persists after trying these steps, it would be beneficial to contact your organization's IT support or Microsoft Support for further assistance. They can analyze the specific environment and provide targeted guidance to resolve the Outlook setup issue.

Best regards,
Priscilla.

Answer 2

Hi @Amos Asthana ,

At the last it is asking to setup outlook profile when I am trying to add then again getting same error like password window popping up again and again.

Do you mean you have tried creating a new Outlook profile, but the issue persisted when trying to add the email account?

At the last it is asking to setup outlook profile when I am trying to add then again getting same error like password window popping up again and again.

To help troubleshoot the problem, please try using the "Test E-Mail Autoconfiguration" service in Outlook and see if the Autodiscover can succeed. (Be sure to remove all personal information like domain name and email address if you need to share the output.)

1. While Outlook is running, click the CTRL key and then right-click the Outlook icon in the system tray, select “Test Email Autoconfiguration”.
2. Confirm that the email address is in the address field, uncheck “Use Guessmart” and “secure Guessmart authentication” boxes. Then click the “Test” button.

Once it runs, check the Log tab.

Besides, based on my experience, you can try testing on one problematic machine by adding the registry keys below and see if it can help:
(Important: Follow the steps in this section carefully. Serious problems might occur if you modify the registry incorrectly. Before you modify it, back up the registry for restoration in case problems occur.)

HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Autodiscover
DWORD: ExcludeLastKnownGoodUrl
DWORD: ExcludeScpLookup
Value: 1

---

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.