SMTP: Response User Unknown
This signature detects SMTP server responses that are generated when an unsuccessful attempt is made to verify an unknown e-mail address using the "VRFY" command. Attackers receive a "550 user unknown" error message.
References
CVE: CVE-1999-0531
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