Question
Why do I receive "RELAY Alert" messages from LFD?
Answer
LFD "RELAY Alert" messages are generally triggered by incoming emails that arrive in quick succession from another mailserver. If enough messages come in from the same IP address or IP-address range to trigger this alert type, you or the server administrator should investigate why the IP address is sending so much mail, as it could be an indicator of incoming spam and may need to be blocked in your server's firewall.
Note: CSF/LFD is third-party software that is not provided or supported by cPanel. For further information on CSF/LFD refer to their README file here:
ConfigServer Security & Firewall