Am 06.10.2023 schrieb Stuart Henderson <s...@spacehopper.org>: > On 2023/10/06 10:09, Marco via mailop wrote: > > Hello! > > > > I have an IPv6 and IPv4 accessible server, both protocols work and I > > receive mails with IPv6 too. > > Although, I see that certain IPv6 capable servers send with IPv4 in > > some cases. > > I am not aware of any outages and the strange things is it is rather > > random which protocol they use. > > > > relay=mx.mailop.org [91.132.147.157] #never sent me mail via IPv6, > > but I can send to them via IPv6 > > relay=bendel.debian.org [82.195.75.100] > > relay=bendel.debian.org [IPv6:2001:41b8:202:deb:216:36ff:fe40:4002] > > > > What can be the reason for that? > > Postfix balances address families by default to avoid blockages if one > isn't working:
Isn't a timeout of some seconds enough for that? Most people have a working connection and most servers too. > https://www.postfix.org/postconf.5.html#smtp_address_preference > https://www.postfix.org/postconf.5.html#smtp_balance_inet_protocols Does the balancing test IPv6 first or is it just randomly? Does it use the first address that works? Then that explains the behaviour. > Perhaps some other MTAs have similar too. All of the MTAs that create that effect use Postfix, so it seems to be related to it. _______________________________________________ mailop mailing list mailop@mailop.org https://list.mailop.org/listinfo/mailop
