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rllaquePeru avatar image
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rllaquePeru asked YukiSun-MSFT commented

Outlook problem connecting to Exchange online mailbox

Hello,

I have a problem with Outlook 365 configured with an Exchange Online mailbox in Windows 10, after working perfectly for several months, suddenly at random times, when Outlook is started, it will not connect (“Trying to connect” appears in Outlook status bar). In the event log the following event appears:

“The Exchange web service request GetAppManifest failed. The error code is 0. HTTP response code: 401
Additional Error Message: An unknown internal error occurred. The error code is 80004005”

The mailbox can be opened perfectly fine in a web browser (OWA) in the same computer, and Outlook 365 with the same account works fine in another (work) computer and on the user's phone.

I've verified the internet connection for the computer and it is working fine, there isn’t any firewall or antivirus installed other than Windows Defender (it’s a home computer). I tried to uninstall and reinstall Office 365 and recreate the profile but the issue persists.

Any ideas of what can be causing the problem?

Thanks,

Ricardo

office-exchange-online-itpro
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1 Answer

YukiSun-MSFT avatar image
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YukiSun-MSFT answered YukiSun-MSFT commented

Hi @rllaquePeru,

after working perfectly for several months, suddenly at random times, when Outlook is started, it will not connect

Any changes were made to the affected mailbox(es) right before the issue started?
In order to help narrow down whether the issue is caused by any third-party add-ins added in the Outlook client, it's suggested to try running Outlook in safe mode(Press Win+R, type "outlook /safe", press Enter.) when the issue occurs and see if Outlook can start properly.

and Outlook 365 with the same account works fine in another (work) computer and on the user's phone.

By this, do you mean the issue is now only affecting a particular account on a particular computer? If this is the case, based on my research on the error you shared above, it could be related to dns, please try running "Ipconfig /release" then "Ipconfig /renew" on the problematic computer and see if there would be any improvement.

Here's a thread which mentions the similar event log in the discussion for reference:
I have a user who has multi-factor sign in and outlook wont accept credentials
Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.
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Hi @rllaquePeru,

I am writing to see how everything is going on with this thread. If you still have further concern on this, please feel free to let us know.


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Hi @YukiSun-MSFT, sorry for the delay and thank you very much for your answer. I tried the solutions suggested but the problem persist, I even tried to change the DNS servers to Google public ones (8.8.8.8, 8.8.4.4) to discard a problem with DNS. The only thing that works is to restart the computer. I am now thinking is this can be a problem with the ethernet network adapter (even if the problem only happens with Outlook). I will try to use a USB Ethernet adapter and see if the issue reappears.

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Hi @rllaquePeru,

Thanks for posting back with the current status of this issue. As regards to your concern about the ethernet network adapter, agree that it's worth testing to see if there would be any improvement.

Besides, I'd suggest trying to run the Microsoft Support and Recovery Assistant on one affected machine when issue occurs, choose Outlook keeps saying "Trying to connect..." or "Disconnected" and see if the tool can help detect anything.


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