> On Feb 5, 2019, at 3:50 PM, Wietse Venema <wie...@porcupine.org> wrote:
>
> If someone registers the domain 'foo', then that is a valid name,
> and they have right to use "helo foo", "mail from:user@foo", and
> so on.
>
> The problem is not sending helo without a dot, the problem is sending
> helo with a name that does not exist.
Returning to the OP's question, Postfix does append $mydomain to
the automatically derived value of $myhostname when the latter
is not explicitly set in main.cf and is not fully qualified.
The OP probably has an explicit unqualified setting of myhostname
in main.cf (perhaps via Debian's: myhostname = /etc/mailname or
similar) and it is not up to Postfix to second-guess such an
explicit setting. If you want Postfix to derive the FQDN,
do not set myhostname at all, set just mydomain, and Postfix
will append that to the system hostname if not an FQDN.
The above assumes that the system hostname is stable, and not
derived via DHCP. In the latter case do set an explicit stable
FQDN for $myhostname.
--
Viktor.
