Log file:
Aug 6 10:09:05 ip-172-31-41-211 postfix/submission/smtpd[16024]: connect from unknown[xxx.xxx.xxx.xx]
Aug 6 10:09:05 ip-172-31-41-211 postfix/submission/smtpd[16024]: lost connection after STARTTLS from unknown[52.77.21.130]
Aug 6 10:09:05 ip-172-31-41-211 postfix/submission/smtpd[16024]: disconnect from unknown[XX.XXX.XXX.XXX] ehlo=1 starttls=1 commands=2