Ticket ID Not Found ErrorsTroubleshoot and resolve The system could not find the ticket ID. (WHMCS 8.4 and later) or Ticket ID Not Found (WHMCS 8.3 and earlier) errors.
Undefined Method Importing ErrorsTroubleshoot and resolve Call to undefined method getRawHeader() errors.
Unregistered Address ErrorsTroubleshoot and resolve The sender's email address is not registered. (WHMCS 8.4 and later) or Unregistered Email Address (WHMCS 8.3 and earlier) errors.