Listing 1: An example session with an SMTP service
S: MAIL FROM:<fazio@danet.com>
R: 250 OK

S: RCPT TO:<someone@someplace.com>
R: 250 OK

S: RCPT TO:<someone.else@elsewhere.com>
R: 550 No such user here

S: RCPT TO:<santa.clause@northpole.com>
R: 250 OK

S: DATA
R: 354 Start mail input; end with <CRLF>.<CRLF>
S: All I want for Christmas...
S: ...etc. etc. etc.
S: <CRLF>.<CRLF>
R: 250 OK