On Thursday, February 21, 2013 10:30:10, Todd Lyons wrote:
> On Thu, Feb 21, 2013 at 6:53 AM, Cyborg <cyborg2@???> wrote:
> > This seems to be a design issue :
>
> It's not an exim design issue. It is a design issue of the SMTP
> protocol. Once you get to the data phase of an smtp email delivery,
> you are only allowed to issue one answer for all intended recipients:
> accept, reject, or defer.
[...]
> > a new acl "acl_per_recipient" could solve such problems on an elegant
> > way.
>
> An experimental proposed SMTP protocol called PRDR (Per Recipient Data
> Responses) from several years back is exactly what you describe. It
> just so happens that Jeremy Harris and I coded up some experimental
> PRDR support and have merged it into the master development branch
> (which leads to the next release of Exim, whenever that turns out to
> be).
>
> It is sparsely tested, but I am running the code on a production
> server and it has not blown up yet, though I'm not really using the
> PRDR acl for anything that the DATA acl doesn't already do.
>
> If you want to test it, you can checkout master, build, install, and
> run it.
I pulled the Exim master and found reference to the expired draft PRDR spec in
/doc/doc-txt/experimental-spec.txt:
http://www.eric-a-hall.com/specs/draft-hall-prdr-00.txt
PRDR requires opt-in by the sending MTA during the MAIL FROM command, and also
changes the response after the DATA command if there are per-recipient
handling differences. This means that it only works with other MTAs that also
implment PRDR, which at the moment sounds very rare.
If the other MTAs implement this it could be very worthwhile, but I'm not sure
what the chances are of the MTAs getting support for this.
-- Chris
--
Chris Knadle
Chris.Knadle@???
