Google Mail OAuth Class "WHMCS\Module\Mail\SmtpOauth" not found Errors


After updating to WHMCS v8.6.0, users of the Google Mail Provider using the OAuth 2 SMTP Authentication setting, may encounter a Class not found error when sending emails:

Class "WHMCS\Module\Mail\SmtpOauth" not found

The email is not sent.


Apply the 8.6.1 Maintenance Release via Utilities > Update WHMCS.


We have created a hotfix for WHMCS 8.6.0 to resolve the error:


  1. Go to Configuration > System Settings > General Settings > Mail Tab.
  2. Click Configure Mail Provider.
  3. Select Password as the SMTP Authentication setting.
  4. Enter your Google Mail account's password or an App Specific Password.
  5. Click Save.

An App Specific Password is required if Two Factor Authentication is enabled on your Google Mail account.