Minimal POP3 Commands: USER name valid in the AUTHORIZATION state PASS string QUIT STAT valid in the TRANSACTION state LIST [msg] RETR msg DELE msg NOOP RSET QUIT Optional POP3 Commands: APOP name digest valid in the AUTHORIZATION state TOP msg n valid in the TRANSACTION state UIDL [msg] POP3 Replies: +OK -ERR Example C: USER mrose S: +OK mrose is a real hoopy frood C: PASS secret S: +OK mrose's maildrop has 2 messages (320 octets)