Microsoft Outlook Classic emails are not operating.

Try these steps in order, starting with the easiest:

1. In classic Outlook, look at the bottom status bar.
   • If it shows Working Offline, go to Send/Receive on the ribbon and select Work Offline to reconnect.
   • If it shows Connected, Outlook is reaching the mail server, so continue to the next steps.
2. Check whether Outlook is busy with another background task.
   • At the bottom of the Outlook window, see whether it is processing something such as send/receive or a large attachment.
   • If so, wait 2 to 3 minutes and see whether Outlook starts working again.
3. Check for a stuck message with a large attachment.
   • Open the Outbox.
   • Start with the oldest message.
   • If it has an attachment larger than 20 MB, remove the attachment and try sending again.
   • A large stuck message can block later messages from sending.
4. Start Outlook in safe mode to check whether an add-in is causing the freezing.
   • Press Windows key + R.
   • Type outlook.exe /safe and select OK.
   • If Outlook works in safe mode, disable add-ins:
     • Open File > Options > Add-ins.
     • Select COM Add-ins > Go.
     • Clear all check boxes, then select OK.
     • Restart Outlook normally.
   • Important: disable add-ins by clearing the check boxes. Do not use Remove.
5. Install Windows and Office updates.
   • Outlook freezing and send/receive problems can happen when updates are missing.
   • Install the latest Windows updates and the latest Microsoft 365 or Office updates.
6. Repair Office.
   • Close Outlook and other Office apps.
   • Open Control Panel > Programs and Features.
   • Right-click Microsoft Office 2016 and select Change.
   • Run the repair.
   • This can take some time.
7. Repair the Outlook profile.
   • If Outlook still freezes or does not sync correctly, repair the Outlook profile or create a new one.
8. Repair the Outlook data file.
   • If Outlook stores mail in a .pst file, run the Inbox Repair Tool.
   • This can fix corruption that stops sending, receiving, or syncing.
9. If the issue started very recently after a Windows update and the account is a POP account, check whether update KB5074109 is installed.
   • Some accepted Microsoft Q&A answers describe a known issue where classic Outlook POP profiles can hang or freeze after that update.
   • If that update is present, uninstalling it and restarting the PC has been suggested.
   • Warning: uninstalling Windows updates can reduce security temporarily, so this should be done carefully.

For limited technical experience, the safest order is: Safe mode test -> updates -> Office repair -> profile repair -> data file repair.

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