Simple Mail Transport Play

S: 220 server.example.com ESMTP
C: EHLO client.example.com
S: 250 OK
................................... filter_relay
C: MAIL FROM:<sales@example.com>
S: 250 OK
................................... filter_sender
C: RCPT TO:<support@example.com>
S: 250 OK
................................... filter_recipient
C: DATA
S: 354 Start Input
C: Help!  I can't send emails!
C: .
S: 250 OK
................................... filter_begin, filter, filter_end
C: QUIT
S: 221 Closing connection