S: [wait for open connection]
C: [open connection to server]
S: 220 mail.example.com ESMTP service ready
C: EHLO example.org
S: 250-mail.example.com
S: 250-SMTPUTF8
S: 250-LIMITS RCPTMAX=20 MAILMAX=5
S: 250-SIZE 100000000
S: 250-8BITMIME
S: 250-ENHANCEDSTATUSCODES
S: 250-PIPELINING
S: 250-CHUNKING
S: 250 STARTTLS