Sample smtp interaction
S: 250 Hello crepes.fr, pleased to meet you
C: MAIL FROM: <alice@crepes.fr>
S: 250 alice@crepes.fr... Sender ok
C: RCPT TO: <bob@hamburger.edu>
S: 250 bob@hamburger.edu ... Recipient ok
S: 354 Enter mail, end with "." on a line by itself
S: 250 Message accepted for delivery
S: 221 hamburger.edu closing connection