Just to help out people who might be googling for this problem, this patch fixes this symptom in the mail logs:
Sep 10 06:44:23 hostname postfix/smtpd[17970]: SSL_accept error from unknown[1.2.3.4]: -1 Sep 10 06:44:23 hostname postfix/smtpd[17970]: warning: TLS library problem: error:1417D18C:SSL routines:tls_process_client_hello:version too low:../ssl/statem/statem_srvr.c:974: Sep 10 06:44:23 hostname postfix/smtpd[17970]: lost connection after STARTTLS from unknown[1.2.3.4] There are certainly live systems out there that trip this.
