SMTP: Missing "HELO"
This protocol anomaly triggers when it detects an SMTP command without a prior HELO command. As all SMTP clients and servers use HELO, this can indicate an attacker or an exploit script manually trying to send commands to an SMTP server.
References
srx-branch-12.3
srx-19.3
srx-branch-19.3
vsrx3bsd-19.2
srx-branch-19.4
vsrx-19.4
mx-12.3
mx-19.4
vmx-19.4
mx-19.3
vsrx3bsd-19.4
srx-19.4
vsrx-12.3
vmx-19.3
vsrx-19.2
srx-12.3