email stooped working

Question

. Our Exchange email has stopped sending and receiving, and Outlook on the web is giving a 500 StartupData error. I need help recovering the administrator account and checking our Exchange service.”

Answer 1

Other users are reporting the same issue, which could be a server-side error. There is currently an Exchange error, and multiple users are also reporting Outlook outages.

https://status.cloud.microsoft/
You can click on "customers can reference https://www.twitter.com/MSFT365Status for additional insights into widespread, active incidents."

Or access the direct link;
https://x.com/MSFT365Status/status/2094455556454920701

The link above is not an official Microsoft site; however, it is related to the post on the official X page reporting the outage.

Answer 2

For this combination of symptoms—mail not sending or receiving in any client, plus Outlook on the web showing a 500 StartupData error—start with tenant and service checks before client troubleshooting.

1. Verify whether the issue is service-wide.
   • If more than one person is affected, go to Microsoft 365 admin center.
   • Open Admin > Service health > View the service health.
   • Check Exchange Online status.
   • If Exchange Online is degraded, mail delivery can be delayed and engineers are already working on it.
2. Confirm the affected admin account still has Exchange Online assigned.
   • In Microsoft 365 admin center, go to Users > Active users.
   • Select the administrator account.
   • Open Licenses and apps and confirm Exchange Online (Plan 1 or Plan 2) is enabled.
   • If it is assigned but the mailbox is still failing, unassign and reassign the Exchange license, then wait for synchronization.
3. Test the mailbox outside the desktop app.
   • Sign in to Outlook on the web to confirm whether the mailbox itself is working.
   • If Outlook on the web also fails, the issue is likely not a local Outlook profile problem.
4. Run Microsoft troubleshooting tools.
   • For Outlook connectivity or send/receive issues, run Support and Recovery Assistant.
   • This is recommended as a first troubleshooting step for Microsoft 365 for business email delivery and Outlook connectivity issues.
   • If using new Outlook for Windows, the classic Outlook troubleshooters do not apply.
5. If Support and Recovery Assistant does not fix it, run admin diagnostics.
   • In the Microsoft 365 admin center, run Diag: Troubleshoot Email Delivery.
   • Enter the sender and recipient addresses and select Run Tests.
   • This requires a Microsoft 365 administrator account and is not available for Microsoft 365 Government, Microsoft 365 operated by 21Vianet, or Microsoft 365 Germany.
6. If the administrator account cannot be recovered through license reassignment and diagnostics, open a support request from the Microsoft 365 admin center.
   • Use Support > New Service Request.
   • This is the escalation path recommended when mailbox or tenant-side issues remain after the standard checks.

If this is instead an on-premises Exchange Server web issue and the 500 error started after installing updates, reinstall the Exchange security update from an elevated Command Prompt using the full path to the .msp file, then restart the server. This applies specifically to Exchange Server cases where Outlook on the web or ECP fails after updates with HTTP 500 errors.

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