[Mailman-Developers] Re: Theoretical way to minimize IO load with MTA supported VERP

[Russell Nelson]

tneff@bigfoot.com writes:
 > "Jay R. Ashworth" <jra@baylink.com> wrote:
 > > I don't see that there *is* any theoretical way to *keep* loads down
 > > with VERP, by it's very nature.
 > 
 > If one was willing to extend SMTP again,

Not necessary.  If you know the remote MTA supports VERP, you can just 
send email like this:

        MAIL FROM: <mylist-owner-@mydomain.com-@[]>
        250 mylist-owner@mydomain.com... Sender ok
        RCPT TO: <johnsmith@aol.com>
        250 johnsmith@aol.com... Recipient ok
        RCPT TO: <joerandom@aol.com>
        250 joerandom@aol.com... Recipient ok
        DATA

In other words, no extensions to SMTP are needed other than an
announcement in the ESMTP banner that the MTA will take responsibility 
for expanding VERP addresses.  My own feeling is that qmail ought to
recognize that it's talking to another qmail server, and send a VERP
envelope sender, and multiple envelope recipients.

There's no reason why mailman couldn't use a bulk mailer which sorts
users by recipient hostname, knows how to recognize qmail, and uses
VERP when it does.  It could issue "EHLO hostname" and look for "VERP"
(for future use) or else just two lines:
250-ns.crynwr.com NO UCE
250-PIPELINING
250 8BITMIME

If just -PIPELINING and 8BITMIME are present, then it could issue
"HELP" and look for the qmail help message:
214 qmail home page: http://pobox.com/~djb/qmail.html

As Barry says, VERP tells you precisely which address is bouncing, but 
it doesn't say why.

-- 
-russ nelson              http://russnelson.com | The problem with do-gooders
Crynwr sells support for free software  | PGPok | and governments is that they
521 Pleasant Valley Rd. | +1 315 268 1925 voice | always think the government
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