/dev/rob0:
> On Mon, Dec 14, 2009 at 01:09:45PM -0500, Victor Duchovni wrote:
> > The relay_domains match list is subject to parent domain matching,
> > and because it defaults to $mydestination, will by default include
> > sub-domains of domains listed in $mydestination. This backwards
> > compatibility should be turned off by all users who don't need it:
> >
> > # Empty
> > relay_domains =
> > # Or
> > relay_domains = <explicit list of domains you want>
> >
> > Best practice is to not use the default value for this parameter.
>
> A lot of folks run into this issue. Will a change of the default be
> considered, perhaps with the Postfix 2.7 release?
Making an incompatible change in default settings that will result
in loss of mail, without giving advance warning for of several years?
That would be unacceptable. When people have been using Postfix by
the rules for years, they deserve better than suddenly ending up
with a broken configuration after upgrade. There are at least a
dozen user interface settings that could be "improved", and the
worst we can do is to break a few of those setting every year.
As an example, when local_recipient_maps (recipient validation)
was introduced, it was guaranteed to cause massive loss of mail.
Before this was introduced, people legitimately listed domains in
mydestination and then used transport maps to hand mail for some
domains to non-local(8) delivery agents. To have the benefit of
address classes and recipient validation without breaking everyone's
configuration, I added a safety feature to "make upgrade" that
appended "unknown_local_recipient_reject_code = 450" if no explicit
setting was present in main.cf. This migration tool was added in
Postfix 2.0, and was removed in Postfix 2.4.
So, if someone proposes that a years-old default setting be changed,
then I ask that they also come up with a migration strategy that
will not result in loss of mail with people who have configured
Postfix in good faith.
Wietse
