SMTP conversation (functions we write)


C: Connect to server.example.com
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, etc
C: QUIT
S: 221 Closing connection