SMTP: Request Error Unknown Command
This protocol anomaly triggers when it detects an unknown SMTP command during the command portion of an SMTP connection. This can indicate an experimental version of SMTP or a backdoor/exploit attempt.
References
srx-branch-12.3
srx-branch-19.3
vsrx3bsd-19.2
vsrx3bsd-19.4
srx-branch-19.4
vsrx-19.4
srx-19.4
vsrx-12.3
srx-12.3
vsrx-19.2
srx-19.3