Am 30.06.2018 um 12:44 schrieb Bjoern Franke:
> according to  since 2.8 postfix uses ipv6 as default for
not "since", "in".
> smtp_address_preference. But as stated in the doc, it is unsafe as
> only IPv6 connectivity is broken, so the safe variant would be any.
The parameter was introduced in 2.8, the default was changed after
noticing the problem.
Look at the subject line.