Hello everyone! Currently I am running into an issue that a (misconfigured) destination mailserver does not accept mail on port 25. It allows a TCP connection but it will not send a greeting. Instead, it expects mail to be send to port 587 which seems to accept both mail with and without starttls.
Looking into the logging of my postfix instance, I can see that it tries to connect to port 25 but the destination mailserver will never reply with a "initial server greeting": Jul 23 15:39:05 smtp postfix/smtp[382]: dns_get_answer: type MX for kuiperschuttingen.nl Jul 23 15:39:05 smtp postfix/smtp[382]: smtp_addr_one: host mail.kuiperschuttingen.nl Jul 23 15:39:05 smtp postfix/smtp[382]: lookup mail.kuiperschuttingen.nl type A flags Jul 23 15:39:05 smtp postfix/smtp[382]: dns_query: mail.kuiperschuttingen.nl (A): OK Jul 23 15:39:05 smtp postfix/smtp[382]: dns_query: reply len=59 ancount=1 nscount=0 Jul 23 15:39:05 smtp postfix/smtp[382]: dns_get_answer: type A for mail.kuiperschuttingen.nl Jul 23 15:39:05 smtp postfix/smtp[382]: begin kuiperschuttingen.nl address list Jul 23 15:39:05 smtp postfix/smtp[382]: pref 10 host mail.kuiperschuttingen.nl/185.104.29.14 Jul 23 15:39:05 smtp postfix/smtp[382]: end kuiperschuttingen.nl address list Jul 23 15:39:05 smtp postfix/smtp[382]: smtp_find_self: not found Jul 23 15:39:05 smtp postfix/smtp[382]: global TLS level: may Jul 23 15:39:05 smtp postfix/smtp[382]: ctable_locate: install entry key kuiperschuttingen.nl:mail.kuiperschuttingen.nl:25: Jul 23 15:39:05 smtp postfix/smtp[382]: smtp_connect_addr: trying: mail.kuiperschuttingen.nl[185.104.29.14] port 25... ... ... Jul 23 15:39:20 smtp postfix/smtp[382]: 9ECFB7800D3: to=<[email protected]>, relay=mail.kuiperschuttingen.nl[185.104.29.14]:25, delay=314, delays=299/0.03/15/0, dsn=4.4.2, status=deferred (conversation with mail.kuiperschuttingen.nl[185.104.29.14] timed out while receiving the initial server greeting) This situation got me thinking, how can I configure to try other ports than port 25 in this instance? Port 25 will not work, but port 587 could work however I do not see postfix trying that port. Sending mail from a gmail accounts appears successful and my guess is because it does try to use port 587 when connecting to the destination mail server. TLS level is on 'may': smtp_tls_security_level = may Thank you in advance for any assistance on this question! Regards, Sebastiaan la Fleur
