S: 220 mail.example.net ESMTP C: EHLO mail.example.org S: 250-mail.example.net Hello example.org [192.0.2.1] S: 250-SIZE 52428800 S: 250-8BITMIME S: 250-PIPELINING S: 250-STARTTLS S: 250 HELP C: STARTTLS S: TLS go ahead