Howdy,
I now have IPv6 routing working along with "inet_protocols = all" in
my main.cf (Postfix 2.9.4). I've noticed that using my outbound relay
(which is load balanced across many machines) will connect with either
protocol with no discernible pattern even to the same destination.
Going by the below from the documentation:
The address type ("ipv6", "ipv4" or "any") that the Postfix SMTP
client will try first, when a destination has IPv6 and IPv4 addresses
with equal MX preference. This feature has no effect unless the
inet_protocols setting enables both IPv4 and IPv6. With Postfix 2.8
the default is "ipv6".
What would dictate the smtp client's fallback (for lack of a better
word) to ipv4 assuming the same destination supports both protocols
(confirmed with telnet when I round-robined back to the same smtp
server)?
Thanks!
(these examples could have been to same destination machine or different)
Apr 6 13:49:53 miniserv.private postfix/smtp[6208]: Untrusted TLS
connection established to smtp.comcast.net[2001:558:fe2d:70::30]:587:
TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)
Apr 6 13:49:54 miniserv.private postfix/smtp[6208]: 905CA3553DE:
to=<f...@example.com>,
relay=smtp.comcast.net[2001:558:fe2d:70::30]:587, delay=1.9,
delays=0/0.01/1.3/0.59, dsn=2.0.0, status=sent (250 2.0.0
mhpz1n00E46N1nS8jhq0d6 mail accepted for delivery)
Apr 6 13:49:54 miniserv.private postfix/qmgr[101]: 905CA3553DE: removed
(snip)
Apr 6 13:53:41 miniserv.private postfix/smtp[6560]: Untrusted TLS
connection established to smtp.comcast.net[76.96.40.155]:587: TLSv1
with cipher DHE-RSA-AES256-SHA (256/256 bits)
Apr 6 13:53:43 miniserv.private postfix/smtp[6560]: C46013554A8:
to=<b...@example.com>, relay=smtp.comcast.net[76.96.40.155]:587,
delay=2.5, delays=0/0.01/1.6/0.91, dsn=2.0.0, status=sent (250 2.0.0
mhto1n0061Cv1Ze8ahtpip mail accepted for delivery)
Apr 6 13:53:43 miniserv.private postfix/qmgr[101]: C46013554A8: removed
