Simple Mail Transfer Protocol

Simple Mail Transfer Protocol
Simple Mail Transfer Protocol (SMTP) packets are closely monitored. An SMTP server
responds to client requests with numeric reply codes and optional human-readable strings.
SMTP application inspection controls and restricts the commands that the user can use as
well as the messages that the server returns. SMTP inspection performs these primary tasks:
■ Monitors the SMTP command-response sequence.
■ Permits only 7 of the 14 SMTP commands (HELO, MAIL, RCPT, DATA, RSET, NOOP,
and QUIT).
■ With ESMTP inspection, an additional eight commands are supported (AUTH, DATA,
EHLO, ETRN, SAML, SEND, SOML, and VRFY).
■ Generates an audit trail. Audit record 108002 is generated when an invalid character
embedded in the mail address is replaced.