SMTP:

HELLO (HELO)

MAIL (MAIL)

RECIPIENT (RCPT)

DATA (DATA)

SEND (SEND)

RESET (RSET)

VERIFY (VRFY)

EXPAND (EXPN)

HELP (HELP)

NOOP (NOOP)

QUIT (QUIT)

TURN (TURN)

POP3:

USER

PASS

QUIT

STAT

LIST

RETR

DELE

NOOP

RSET

TOP

UIDL

APOP