Fix: Failed to Verify the Server Certificate Mac Mail

While using Mac Mail, you may receive the following error while opening Mail or adding a new email account.

Connecting Insecure

Failed to verify the server certificate. This could be because of your network configuration or your proxy settings.

 *Update* - This is likely caused by Avast Web Filtering being enabled and blocking Gmail web access for adding a mail account in Mac Mail. Open Avast Security and go to Preferences -> Web Shield -> Disable

If nothing has changed on your Mac to cause this error, try the following.

1. Click the reconnect circle  next to your email account. Sometimes this error appears if you are in a poor area for a wireless network connection. Reconnecting to your email account or quitting and re-opening Mac Mail sometimes fixes this.

2. Sometimes, your email providers SSL certificate for email does not update or auto-update itself in your Keychain. You can try to manually removing it and see if you can re-add your email account with the new SSL certificate.

3. In Spotlight, search for Keychain Access and open it.

4. Under Keychains select login. For category select certificates. Now, look for any certificate with a red x that would be for an email account. Right-click the certificate and select delete.

Note: If you do not see any certificates with a red x, then you do not have to worry about this.

5. Restart Mac Mail.