Why Is My Outlook Classic Asking for Credentials Every Few Minutes in 2025?

How Can I Stop the Annoying "Add a Service" Popup in Microsoft Outlook Classic?

I've been helping IT professionals tackle tricky Microsoft Outlook problems for years. Today, I want to share a frustrating issue that's been hitting Outlook Classic users since mid-June 2025. This problem is causing real headaches for administrators, and I think you need to know about it.

What's Actually Happening

Starting June 13, 2025, something weird began occurring with Microsoft Outlook Classic. Users can start Outlook normally and send emails just fine. But then, after about 1-2 minutes, a popup appears with the title "Add a service." This dialog asks for credentials and claims no work or school account was found with the email address.

Here's the kicker - no matter what credentials you enter, nothing works. If you close the window, Outlook gets disconnected from Exchange. You have to restart Outlook, and the cycle repeats itself.

The Technical Details I've Gathered

This issue first showed up in enterprise environments running:

• Exchange Server 2019 at one location
• Exchange Server 2016 upgraded to 2019 at another location
• Outlook clients from Office 2016, 2019, and 2024

Initially, only Outlook 2024 was affected. But by June 25, 2025, the problem spread to Outlook 2016 and 2019 versions too. What makes this particularly puzzling is that it only affects individual clients - not entire organizations.

Troubleshooting Steps That Haven't Worked

IT teams have tried everything I would normally recommend:

• Deleting login vaults
• Creating new Outlook profiles
• Removing old devices from Microsoft accounts
• Installing latest Office updates
• Adjusting registry values
• Deactivating data protection settings
• Reinstalling Office (temporary fix only)
• Uninstalling CoPilot app
• Switching off cache mode
• Not loading shared mailboxes

The most successful approach has been reinstalling Office without current patches, but this only works temporarily and doesn't solve the root cause.

The Strangest Discovery

Here's where things get really bizarre. When IT professionals used Fiddler (a web debugging proxy tool) to monitor network traffic and diagnose the problem, the popup stopped appearing entirely. This suggests the issue might be related to how Outlook handles certain network connections or authentication processes.

What Microsoft Support Is Saying

Unfortunately, Microsoft's support response has been minimal. Their main suggestion involves setting specific registry values to 0 and restarting clients. This approach hasn't resolved the issue for most affected users.

Why This Matters for Your Environment

This isn't an isolated incident. Multiple forum posts and support cases describe identical symptoms:

• Constant "Add a Service" popups
• Credential requests that never succeed
• Temporary disconnection from Exchange
• Affects only select clients in enterprise environments

The pattern suggests this could be related to a specific Office update or change in Microsoft's authentication systems that occurred around June 13, 2025.

My Recommendations Right Now

Immediate Actions

• Document which specific Office versions and build numbers are affected
• Note the exact timing when the popup appears
• Check if the issue correlates with any recent Office updates
• Monitor whether the problem spreads to additional clients

Temporary Workarounds

• Reinstall Office without the latest patches (temporary solution)
• Consider using Fiddler as a diagnostic tool (though this isn't practical long-term)
• Keep detailed logs for Microsoft support cases

Long-term Strategy

• Escalate support cases with Microsoft
• Connect with other IT professionals experiencing similar issues
• Consider delaying Office updates until a fix is available

What I Think Is Really Going On

Based on the evidence, this appears to be an authentication-related bug introduced in a recent Office update. The fact that Fiddler prevents the popup suggests it's related to how Outlook communicates with Microsoft's authentication services.

The timing (June 13, 2025) and the selective nature of the problem point to a gradual rollout of a problematic update or server-side change that's affecting certain configurations more than others.

I believe Microsoft needs to acknowledge this as a known issue and provide a proper fix rather than suggesting basic troubleshooting steps that clearly aren't working.