In dovecot conf, for submission relay, I've config'd
submission_relay_host = lan.example.com
submission_relay_port = 465
hostname -- not IP -- must be used, to inform relay for cert verification match.
Here,
host lan.example.com
lan.example.com has address 10.0.1.47
lan.example.com has IPv6 address fd80:25:01::47
The receiving smtp relay listens only on IPv4 -- no IPv6 service,
telnet 10.0.1.47 465
Trying 10.0.1.47...
Connected to 10.0.1.47.
Escape character is '^]'.
telnet -6 fd80:25:01::47 465
Trying fd80:25:01::47...
telnet: connect to address fd80:25:01::47: Connection refused
On the lan, all boxes are set, in "/etc/gai.conf", for IPv6 to take precedence
over IPv4.
On submission to dovecot submission port, after login/auth, dovecot smtp-client
subsequently connects to the relay
lan.example.com:465
IPv6 1st, & fails
2020-10-15 12:51:45 submission(m...@example.com)<8OJP+rqxuvho7Z95>:
Error: smtp-client: conn lan.example.com:465 ([fd80:25:01::47]:465) [1]:
connect(lan.example.com:465) failed: Connection refused
then falls back to IPv4, and continues OK
2020-10-15 12:51:45 submission(m...@example.com)<8OJP+rqxuvho7Z95>:
Info: Successfully relayed message: from=<t...@remote.example.com>, size=84,
id=LMe...Aw, nrcpt=1, reply=`247 2.0.0 Ok: queued as 4CC0KY1wXNzWf93'
not fatal, but wasted effort, and noise in the logs.
how/where do I configure (just) the dovecot smtp-client ->
submission_relay_host to only connect IPv4?
