miss addressed mail

[Paul Howarth]

On Fri, 2004-11-05 at 03:13, Alexander Dalloz wrote:
> Am Fr, den 05.11.2004 schrieb Ow Mun Heng um 4:05:
> 
> > > (note: some mail servers, notably qmail, always send mail to a single 
> > > recipient at a time even if there are multiple recipients for the mail at a 
> > > domain, and others can be configured to do so. Whilst this is very 
> > > inefficient, particularly for large messages, mail you receive from such mail 
> > > servers should always cause your mail server to add the "for" clause in the 
> > > Received: header)
> > 
> > Does sendmail has the same behavior. I would like to know as well since
> > it _is_ very inefficient.
> 
> No, Sendmail sends multiple "RCPT TO:" with one mail.
> 
> sendmail[31362]: iA539ZvT031349: to=<foo at uni-x.org>,<bar at uni-x.org>,
> ctladdr=<alexander.dalloz at uni-bielefeld.de> ...

It can sometimes be useful to get sendmail to send mail separately for
each recipient at a domain though. For instance, if you're running a
mailing list (with Bcc'ed recipients) and you're getting bounces from a
site that doesn't show the envelope recipient address as the address
being rejected (e.g. some MTAs will map the recipient address to a "full
name" before deciding if the mail is deliverable, and then say that mail
to "full name" is undeliverable), this can result in problems finding
the address that is bouncing in order to remove it from the list. By
having the mail sent one recipient at a time, the recipient address may
get added to a Received: header and this may help identifying the bad
address.

The way I do this in sendmail is:

1. Add a new mailer "sesmtp" to (the end of) my sendmail.mc, which
delivers mail to a single recipient at a time:

MAILER_DEFINITIONS
Msesmtp,	P=[IPC], F=DFMuXa, S=EnvFromSMTP/HdrFromSMTP, R=EnvToSMTP,
E=\r\n, L=990,
		T=DNS/RFC822/SMTP,
		A=TCP $h

(this is just a copy of the esmtp mailer without the "m" flag to
indicate that it can deliver to multiple recipients)

2. Add a mailertable entry to have mail to the suspect's domain sent
using this new mailer:

bigfoot.com	sesmtp:bigfoot.com

So all mail to bigfoot.com gets sent in separate emails and I have a
chance if figuring out which bigfoot address is forwarding somewhere
that bounces.

Paul.
-- 
Paul Howarth <paul at city-fan.org>