back into the fold

[Matthew Seaman]

On Mon, Jul 22, 2002 at 10:59:33PM +0100, pao at panforte.org.uk wrote:

> I am using dialup to Freeserve via userland ppp and consequently
> dynamic IP addressing.
> 
> Fetchmail is is pulling my domain (panforte.org.uk) mail from my
> service hosting provider (oneandone.co.uk).
> 
> These two items seem to be fine.
> 
> However when I send email out from my PC,  although I have sendmail
> configured to masquerade the envelope addresses.  If I try to send
> myself a mail to:  pao at panforte.org.uk - the SMTP transaction fails
> with:
> 
>    ----- The following addresses had permanent fatal errors -----
> pao at panforte.org.uk
>     (reason: 550 rejected: cannot route to sender <pao at luthien.cats>)
> 
>    
> This comes from the SMTP server receiving the email.  Not all SMTP
> servers are doing this to me but it is a tad frustrating.
> 
> It appears to me that the SMTP server as part of an anti spam measure is
> checking back through the received lines of the mail envelope and
> spotting the following:
> 
> Return-Path: <pao>
> Received: (from pao at localhost)
>         by luthien.cats (8.11.6/8.11.6) id g6MIxGA00500
>         for pao at panforte.org.uk; Mon, 22 Jul 2002 19:59:16 +0100 (BST)
>         (envelope-from pao)
> 
> 
> Anyhow - can anyone tell me how to configure sendmail to erm break the
> RFC standards and either lie about the received path or alternatively
> pick up and use my allocated dns entry from Freeserve ie:
> dialup-3456.pol.co.uk    - or whatever they use these days?

Well, there's two possible answers to that:

i) Do you forward all your outgoing e-mail through a "Smart Host" at
your ISP?  Probably a good idea as many mail servers will refuse
e-mail from netblocks known to contain dial-up addresses.  See
http://www.mail-abuse.org/dul/ for an example.  There are several DUL
lists done by various people, some freely available others for pay.

However, if you're getting blocked because of this I'd expect you to
get messages saying why.

ii) What does your mail server announce itself as in the SMTP dialog
--- eg:

happy-idiot-talk:~:% mail -v -s test matthew 
test message
.
EOT
matthew... Connecting to localhost.infracaninophile.co.uk. via relay...
220 smtp.infracaninophile.co.uk ESMTP Sendmail 8.12.5/8.12.5; Tue, 23 Jul 2002 07:18:25 +0100 (BST)
>>> EHLO happy-idiot-talk.infracaninophile.co.uk
250-smtp.infracaninophile.co.uk Hello localhost.infracaninophile.co.uk [IPv6:::1], pleased to meet you

The name used in the EHLO or HELO line is what I mean.  It should be
resolvable on the internet by the hosts you want to communicate with.

(Of course, that example is rather contrived, since the output comes
from the smmsp sendmail server on my machine, but the principal is the
same.)

To override what sendmail chooses for itself, you can add:

    define(`confDOMAIN_NAME', `smtp.yourdomain.co.uk')dnl

to your .mc file, or set the j macro in sendmail.cf:

    Djsmtp.yourdomain.co.uk

You could possibly just use straight `panforte.org.uk' as your domain
name, but test thoroughly.  I suspect that many mail servers will
refuse e-mail if your EHLO announced name doesn't resolve to the IP
number you're connecting from.  In that case, you're getting into
dynamic-DNS territory: you'll need to find a service provider that
will let you update an A record to resolve to the IP number you just
got from your dial-up.  The address used doesn't have to be anything
to do with your domain, just resolvable on the internet.

Or get yourself a fixed address.

	Cheers

	Matthew


-- 
Dr Matthew J Seaman MA, D.Phil.                       26 The Paddocks
                                                      Savill Way
Tel: +44 1628 476614                                  Marlow
Fax: +44 0870 0522645                                 Bucks., SL7 1TH UK