C: EHLO client.example.com. S: 250-smtp.server.com Hello client.example.com. S: 250-SIZE 1000000. S: 250 AUTH LOGIN PLAIN CRAM-MD5 C: AUTH PLAIN S: 334. C: dGVzdAB0ZXN0ADEyMzQ= S: 235 2.7.0 Authentication successful .