microsoft 365 outlook classic error 0x80070057

Hello Kevin Williams

I understand how frustrating it is when you can receive emails but are blocked from sending them, especially after you've already put so much effort into troubleshooting.

Have you already tried Q&A Assist suggestion? In addition, please try the following:

1, Disable antivirus email scanning

• Temporarily disable only the "Email Scanning" feature in your antivirus settings (do not disable your entire firewall or real-time protection).
• Try to send a test email. If it works, you may need to keep this feature off or check for an update from your antivirus provider.

2, Perform a clean boot

• Press Windows Key + R, type “msconfig”, and press Enter.
• On the “Services” tab, check “Hide all Microsoft services”, then click “Disable all”.
• On the “Startup” tab, click “Open Task Manager” and “Disable” all startup items.
• Restart your computer and try sending an email in Outlook.

This helps isolate if a third-party application is causing the conflict.

3, Run the "sfc /scannow" Command

• Type “cmd” in the Windows search bar, right-click “Command Prompt”, and select “Run as administrator”.
• Type “sfc /scannow” and press Enter.
• Wait for the process to finish. If it repairs files, restart your PC and test Outlook again.

4, Verify SMTP Port and Encryption

• In Outlook, go to “File” > “Account Settings” > “Account Settings”.
• Select your Gmail account and click “Change” > “More Settings” > “Advanced”.
• Ensure the “Outgoing server (SMTP)” is set to 587 with STARTTLS (or 465 with SSL/TLS).
• On the “Outgoing Server” tab, ensure “My outgoing server (SMTP) requires authentication” is checked.

Warning: Please be careful when modifying registry keys or system settings.

Please feel free to let me know how it goes after trying these steps. Thank you for your understanding.

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Follow these steps focused on Outlook Classic with a Gmail account:

1. Confirm basic connectivity
   • Make sure the PC is online and can reach external sites such as http://www.microsoft.com or http://www.bing.com using a browser. If not, fix network issues first using the guidance in Fix network connection issues in Windows.
2. Check for sync/send issues in Outlook
   • In Outlook Classic, go to the View tab on the Ribbon.
   • Use the Sync button to manually send/receive.
   • Watch the status bar for any additional error messages while Outlook is syncing. For more detail, see Sync to manually check for new mail and to send messages in Outlook.
3. Verify password and app password usage
   • If the Gmail password was changed recently on the web, update it in Outlook as well. For general password reset guidance, see Reset a forgotten Microsoft account password.
   • If Gmail is configured to require an app password (for example, when 2‑step verification is enabled and “less secure apps” are blocked), ensure Outlook is using the Google app password, not a Microsoft app password. A similar issue was resolved when a user discovered Outlook Classic was using a Microsoft app password instead of the correct Google app password.
   • Generate a Gmail app password in the Google account security settings, then paste that app password into Outlook when prompted for the account password.
4. Repair the Outlook installation
   • Since reinstall and update were already done, run a repair specifically:
   • Use the Office repair process described in Repair an Office application. This can fix underlying Outlook components that affect sending.
5. Repair or recreate the Outlook profile
   • A corrupted profile can allow receiving but fail on sending.
   • Follow Fix your Outlook email connection by repairing your profile to repair the existing profile.
   • If repair does not help, create a new profile using Create an Outlook profile and re-add the Gmail account with the correct app password.
6. Start Outlook in Safe Mode to rule out add‑ins
   • Some add‑ins can interfere with sending.
   • Press the Windows key, type outlook.exe /safe, and press Enter.
   • Try sending an email in Safe Mode. If sending works, keep using the new profile and disable problematic add‑ins as needed.
7. Check antivirus email scanning
   • Some antivirus products scan outgoing mail and can block sending if they detect an issue.
   • If antivirus email scanning is enabled, temporarily disable only the email‑scanning feature (not real‑time protection) or consult the antivirus help desk as suggested in the Outlook guidance.

If, after these steps, sending still fails with 0x80070057, focus on confirming that Gmail’s SMTP settings and app password are correct and that the Outlook profile was recreated after fixing those credentials, as credential/app‑password mismatches are a common cause when receiving works but sending fails.

References:

• I can't send or receive messages in Outlook
• I can't send or receive messages with Outlook for Mac
• search for solutions another user has found
• How can I get office 365 to work? - Microsoft Q&A
• Outlook is using a temporary email and I cannot receive emails - Microsoft Q&A
• Detected a problem launching new Outlook - Microsoft Q&A
• Outlook ask for credentials every minute - Microsoft Q&A