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We are using Office 2016 with Exchange 2029 on-premises. Since Office 2016 is end of support soon, I am working on moving to Office LTSC 2024 (management prefers Office LTSC 2024 over MS 365).
Currently, I am testing Office LTSC 2024 on couple PCs. When opening Outlook (Classic), the Microsoft window “Add a Service” keeps popping up. It is pre-filled with user@domain.local and says “We couldn’t find a work or school account with that email address”. On the Outlook window status bar, it says “need password”. If I close the “Add a Service” window and click on “need password”, Outlook is connected fine to our Exchange server on-premises. But after a few minutes, the “Add a Service” window will come back again frequently.

I did some research some users said the fix is to uncheck all the Connected Services.

I already checked: no connected services are selected, no optional connected experiences are selected.

What is the fix for this issue?

Thank You so much for your input.

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Hopefully, you meant to say Exchange 2019?

That aside, you REALLY need to get management to understand that on-prem Exchange/Office is as good as dead and getting off now, while there’s still people to help you is critical…not to mention Classic Outlook, too, is on the way out.

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This is a known and common issue for a misconfigured exchange server, you need to check and confirm your autodiscover is correct.

I will also note that while Office 2016 is end of life on October 14th of this year, so is exchange 2019, if 365 is not on the cards, you need to upgrade to Exchange server 2025 SE (subscription edition) unless you want to continue running unsupported and possibly vulnerable software.

Start by confirming your autodiscover is correct and valid and does not have an expired or misconfigured SSL certificate.

Check the authentication settings.

Step 2, look at upgrading your exchange or keeping Office 2024 with an exchange online plan, either way, on-prem of hosted you need a new subscription.

domain.local is no longer a recommended or best practice, hopefully you have at least added a UPN for your users.

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Outlook classic comes with Office 2024, it’s only outlook 365 where the new outlook applies.

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Yes, we are aware of Office 2016 and Exchange 2019 end of life. That’s why we are working to upgrade to Office 2024 and soon to Exchange SE.

Rod-IT,
Currently, Exchange 2019 is working fine with Outlook 2016, so I assume Autodiscover, authentication, and SSL certificate should be configured correctly.

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You should never assume, It’s OK to be unsure, but never just assume because it worked with one, it should work with another.

Office 2016 isn’t designed to be cloud-first, and defaults to basic authentication, 2024 defaults to modern authentication (OAuth2.0) and is designed to be cloud-first.

The error you are getting is because something isn’t configured correctly, as I noted, start with your autodiscover URL and SCP record, both internally and externally.

This is another big clue, that is is unable to find your domain service records, it’s trying the cloud and failing.

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