what AI says
"Error 3253 in Outlook for Mac indicates that the connection to the email server failed or was dropped, typically preventing outgoing email while allowing incoming messages. This is often resolved by updating Outlook, adjusting server port settings, disabling antivirus "email shields," or clearing the Outlook cache. ![]()
Microsoft Learn
+3
Top Solutions for Error 3253
- Update Outlook for Mac: Open Outlook, go to Help > Check for Updates to ensure you are running the latest version, then restart the application.
- Disable Antivirus/Email Shield: Third-party antivirus software (e.g., Avast, AVG) can cause this error by blocking outgoing mail. Temporarily disable "Email Shield" or "Web Monitor" to see if it resolves the issue.
- Verify Port Settings: Check your outgoing (SMTP) server settings.
- Navigate to Tools > Accounts in Outlook.
- Ensure the outgoing port is correct (often
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- or
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- ) and that SSL/TLS is enabled if required by your provider.
- Clear Cache (Exchange/IMAP): If you use Exchange or IMAP, right-click (or Ctrl-click) your folder, select Properties > General > Empty Cache to force a resync.
- Rebuild Database: Use the Microsoft Database Utility to repair potential corruption in your Outlook profile.
Other Potential Causes
- Large Emails: An email with a large attachment stuck in the Outbox can drop the connection.
- Unstable Internet: The connection might be dropping during server authentication.
- Incorrect Server Authentication: Verify that your username and password are correctly configured for the outgoing server.
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what microsoft says
Outlook for Mac Help - Microsoft Support
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Error 3253 Connection to the server failed - Google-
