Hallo,
postbank.de is known (to me) as broken somehow. Today I noticed delivery problems to dslbank.de That focused my attention again to that unsolved issue.
$ posttls-finger dslbank.de posttls-finger: warning: DANE TLSA lookup problem: Host or domain name not found. Name service error for name=_25._tcp.mailrelay1.bonn.postbank.de type=TLSA: Host not found, try again posttls-finger: warning: DANE TLSA lookup problem: Host or domain name not found. Name service error for name=_25._tcp.mailrelay1.bonn.postbank.de type=TLSA: Host not found, try again posttls-finger: Failed to establish session to dslbank.de via mailrelay1.bonn.postbank.de: TLSA lookup error for mailrelay1.bonn.postbank.de:25 posttls-finger: warning: DANE TLSA lookup problem: Host or domain name not found. Name service error for name=_25._tcp.mailrelay2.bonn.postbank.de type=TLSA: Host not found, try again posttls-finger: warning: DANE TLSA lookup problem: Host or domain name not found. Name service error for name=_25._tcp.mailrelay2.bonn.postbank.de type=TLSA: Host not found, try again posttls-finger: Failed to establish session to dslbank.de via mailrelay2.bonn.postbank.de: TLSA lookup error for mailrelay2.bonn.postbank.de:25
$ postconf mail_version mail_version = 3.0.3
$ postconf smtp_tls_security_level smtp_tls_security_level = dane
$ dig _25._tcp.mailrelay1.bonn.postbank.de tlsa
... ;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 20811 ;_25._tcp.mailrelay1.bonn.postbank.de. IN TLSA ...
-> SERVFAIL is the problem here.
$ which_resolver_do_i_use unbound-1.5.x @ localhost
But I wonder why dane.sys4.de tell me "No TLSA records." In fact there is some magic @sys4 that understand, postbank.de do not publish TLSA records. postfix do not know this magic and leave messages undelivered in my queue :-/
OK, I will now add the next whitelist entry to smtp_tls_policy_maps but that's no generic solution. Any hints are appreciated.
Thanks, Andreas