Lorenzo Bernardi:
> Hi Wietse,
>
> Thank you for your answer.
>
> The docker containers are running Debian 9.3 and the postfix package
> from the official Debian repository (Version: 3.1.6-0+deb9u1).
>
> As you can see below the source code still contains calls to
> gethostbyname():
Grep does not prove that code is called. The only gethostbyname
calls that are left over in the code are in src/local/biff_notify.c
and in src/util/find_inet.c, and the latter is called only by the
dict_mysql.c module. None of these calls are relevant for the problem
at hand: hooking up Postfix with the Dovecot auth service.
> Regarding the docker network, I followed the recommendations of the
> official website and I'm using a user-defined network, which works with
> no issue.
You made a mistake somewhere, because the SYSTEM LIBRARY FUNCTION
getaddrinfo() is unable to find your dovecot host unless you add
it to /etc/hosts.
To be totally clear about this: Postfix does not look in /etc/hosts,
it is the SYSTEM LIBRARY that reads the file, as configured in the
SYSTEM CONFIGURATION file /etc/nsswitch.conf.
See www.postfix.org/DEBUG_README.html for how to trace a program
with strace and ltrace, then you can see which call is failing and
why.
Wietse
