[Mailman-Developers] Re: way to minimize IO load with MTAsupported VERP

[Dan Mick]

Nigel Metheringham wrote:
> It would be nice
> if there was some form of spec for it though - there appears to be one
> for a VERP extension on the courier site, but thats using a VERP keyword
> and not XVERP (presumably they are just about the same, but one you
> don't need to clear with the ESMTP spec gurus).

The bottom of http://www.courier-mta.org/ links that VERP proposal
behind the name XVERP.  I'm sure that the X is there simply to allow
its presence and use before the RFC reaches some consensus.

A thing I hadn't thought about: if the local MTA senses that the remote
MTA *also* supports XVERP, it doesn't have to do the expansion
itself; it can simply send on one XVERP-ed multirecipient message,
and let the final MTA handle the envelope multiplication.