Using classic Outlook for Windows in business environments
Microsoft is currently reporting a Microsoft 365 service degradation affecting Outlook and Exchange Online mail access; monitor the incident in Service health because the latest update and restoration estimate will be posted there.^1^
Check your organization’s status
If you are a Microsoft 365 administrator:
- Sign in to the Microsoft 365 admin center.
- Go to Health → Service health.
- Under Active issues Microsoft is working on, open the Outlook or Exchange Online incident.
- Review User impact, Status, Last updated, and All updates for Microsoft’s current progress and any estimated restoration time.
- Select Manage notifications for this issue if you want status updates by email.^2^
If the admin center is inaccessible, continue checking the public Microsoft service-status page linked above.
What to do now
- There is no confirmed resolution time in the available public information. The incident details in your tenant’s Service health dashboard are the authoritative source for restoration updates.
- Avoid deleting Outlook profiles, removing accounts, reinstalling Office, or changing registry settings while a matching Exchange Online incident remains active. Those actions do not resolve a service-side outage.
- If Outlook on the web is available, it can be used temporarily. If both Outlook desktop and the web mailbox fail, wait for the service incident to be restored.
- If you are not an administrator, contact your organization’s IT team and ask them to check Health → Service health.
If no matching incident appears
An administrator should select Report an issue on the Service health page. For delivery-specific failures, run Diag: Troubleshoot Email Delivery in the Microsoft 365 admin center. If only one mailbox is affected, compare Outlook desktop with Outlook on the web; receiving mail on the web but not in Classic Outlook indicates a client or profile issue rather than organization-wide mail flow.^3^
When reporting the problem, include:
- The approximate start time and time zone
- Number of affected users
- Whether Outlook on the web also fails
- The exact error message and code
- Whether sending, receiving, sign-in, or all mailbox access is affected
References