Viktor Dukhovni:
> On Wed, Nov 23, 2011 at 09:11:55AM -0500, Wietse Venema wrote:
>
> > To make per-recipient end-of-data replies useful with Postfix, PRDR
> > would need to be supported by at least one third-party content
> > inspection mechanism (such as Amavisd-new or Milter), because I see
> > no obvious user interface for PRDR with Postfix header/body_checks.
>
> My concern is that there is no obvious mechanism by which one may
> determine that a transparent (formerly) SMTP proxy filter is actually
> ready to support PRDR. Certainly the filters of this type that I wrote
[and other SMTP-like engines in firewalls, anti-virus, and so on.]
The sysadmin will learn immediately that a proxy-based content
filter doesn't support PRPR. The filter will flag the post-filter
SMTP server's 3XX reply after "." as a protocol error.
As for stuff-in-the-middle elsewhere in the infrastructure that
makes incorrect assumptions about the protocol, those assumptions
would have to be corrected. Meanwhile, Postfix has mechanisms to
filter out EHLO keywords, that can mitigate such problems.
Wietse
