Subject: Re: [ietf-smtp] Reviving PRDR

From: Phil Pennock <[email-masked]>
Date: Sat, 30 Mar 2019 19:07:22 -0400

Deliberately breaking thread because distinct sub-topic, but what I'm
saying is I think very relevant to IETF SMTP.

On 2019-01-10 at 23:43 +0000, Дилян Палаузов wrote:
> Last time PRDR was discussed here was 2014.  Since 2013 it is integrated in Exim and back in March 2014 it was not
> enabled by default.  Today in Exim enable_prdr still defaults to False in the documentation, but the
> src/configure.default sets it to true.
> 
> Why isn’t enable_prdr in Exim enabled nowadays by default?

Exim tends to be a little cautious in how new protocol features,
especially not-standards-track protocol stuff, gets introduced.
Local lookup sources?  Throw them in easily, nobody else's business but
the site operator.  Protocol?  We've never rushed there.

PRDR has now moved to where support will be compiled in by default in
the next release of Exim, and the builder has to choose to explicitly
disable the feature.  Actually advertising PRDR still needs to be
explicitly turned on, but the default/example configure file will now do
so.

Jeremy Harris has done almost all of the hard work here but AFAIK all of
the Exim maintainers are entirely on board with PRDR rolling out.  I
know I am.

-Phil