On Mon, Sep 22, 2014 at 11:41:00AM -0400, Wietse Venema wrote:
> This time PLEASE refrain from sidetracking the discussion. I want
> to know what will break when the default changes, if that is not
> too much to ask for.
>
> Summary:
>
> Until now, Postfix has a default setting "append_dot_mydomain = yes".
> This performs autocompletion from user@host to user@host.$mydomain.
> But this default setting is becoming problematic.
>
> I need to find out what will break when the default is changed to "no".
My main concern is with "user@machine" non-fqdn address forms
leaking out of minimally configured clients to then to be rejected
by the smarthost mail hub, at which point they send non-fqdn bounces,
which are also rejected, and the mail disappears when even the
postmaster copy is rejected.
I guess over the years I've drunk the Postfix backwards compatibily
coolaid, and my gut sense is that while an occasional "@localhost.com"
(reported for the first time in well over a decade) may be a problem,
that this is not worth the backwards-compatibility cost.
Postfix upgrades have been remarkably frictionless over the years,
and I'm not convinced this issue deserves a compatibility break.
There are probably also books and many HOW-TO documents that assume
"append_dot_mydomain = yes", and updating either can be non-trivial.
So my preference would be to just add documentation warnings about
defaulting both "mydomain" and "append_dot_mydomain". Preferrably
at least one of these has an explicit value in main.cf.
A warning from trivial-rewrite(8) when both are defaulted might be
enough to get most folks to add the appropriate safety-net for
themselves.
--
Viktor.
