220 Debatable SMTP 0.2 Ready.
HELO

250 OK Welcome
HELO

250 OK Welcome
DATA

503 start with 'mail from: ...'
HELP

214-Commands

214-DATA EXPN HELO HELP MAIL
214 NOOP QUIT RCPT RSET VRFY
NOOP

250 Whatever.
RSET

250 buffahs ah cleah, suh!
VRFY

252 Nice try.
EXPN

252 Nice try.
MAIL

501 could not find name@postoffice in <>
RCPT

553 no user@host addresses found in <>
QUIT

221 Ciao