Troubleshoot and resolve transactions that the system isn't recording.
Troubleshoot 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.
Troubleshoot and resolve issues with sending general emails to clients.
Troubleshoot and resolve issues with ticket notification emails.
Troubleshoot and resolve issues with welcome emails not sending.
Troubleshoot and resolve Unsupported Protocol errors.
Troubleshoot and resolve Make certain that you have selected a valid Update Channel and then try again errors.