572 billycan.freeserve.co.uk host name is unknown

The mail has been sent from your local machine to Freeserve's inbound mailserver:

Received: from modem-31.anfauglir.dialup.pol.co.uk ([62.136.109.159] helo=billycan1)
by cmailg3.svr.pol.co.uk with smtp (Exim 4.14) id 1C2VzJ-0008MM-WC
for mplatten@genmail.net; Wed, 01 Sep 2004 15:21:27 +0100

...and then on to Freeserve's outbound mailserver:

Received: from [195.92.195.173] (helo=cmailg3.svr.pol.co.uk)
by fmailm2.svr.pol.co.uk with esmtp (Exim 4.14) id 1C2VzN-0000Az-S4
for mplatten@genmail.net; Wed, 01 Sep 2004 15:21:29 +0100

... which contacted Genmail's mailserver and said "I've got some mail for you from simon@billycan.freeserve.co.uk".

Genmail's mailserver rejected the mail with a 572 error, and the message 'hostname is unknown'.

Odd, that, since a 572 error is strictly 'Relay not authorised', not 'hostname is unknown' - and usually only happens when something tries to send mail via a gateway that doesn't accept, or relay, mail for the intended recipient.

Here's what I guess is going on - Genmail have got "VisNetic MailScan for SMTP" installed, a content-filtering mail gateway add-on (I've found this out by trying to connect to the mailserver for genmail.net by hand).

This software can be configured to reject inbound mail based on a number of tests, eg by doing what's called an MX lookup ("Is there a Mail eXchanger record that says there's a machine somewhere on the internet that's prepared to accept mail for the Sender's email address simon@billycan.freeserve.co.uk?" - to which the answer is 'yes') and/or an A record lookup ("Is there an IP address for a machine on the internet called billycan.freeserve.co.uk" - to which the answer is 'no').

From what I can tell, Freeserve advertise an MX record for your billycan.freeserve.co.uk address (it's a machine called mail-in.freeserve.com), but don't give billycan.freeserve.co.uk an A record (host not found). This is perfectly valid for them to do - the bit after the @ sign in an email address doesn't have to be a machine with an IP address.

The problem therefore is with Genmail's configuration of their inbound mail gateway - it's rejecting mail when it can't find an IP address for the domain part of an email address.

However, this bounce is from September and I've just tested the Genmail server by hand and it doesn't *seem* to be suffering the problem any more. If it was, it'd reject the following test with a 572 error immediately after the MAIL From: line

$ telnet reliance.gen.net.uk 25
Trying 213.249.192.9...
Connected to reliance.gen.net.uk.
Escape character is '^]'.
220 Welcome to gen.net.uk - MailScan ESMTP Server BUILD 5.2.86
EHLO anubis.novacaster.com
250-Hello anubis.novacaster.com! Pleased to meet you.
250-8BITMIME
250-DSN
250 HELP
MAIL From: <simon@billycan.freeserve.co.uk>
250 OK - mail from <simon@billycan.freeserve.co.uk>
RCPT To: <mplatten@genmail.net>
250 OK - Recipient <mplatten@genmail.net>
QUIT
221 Service closing transmission channel
Connection closed by foreign host.

What happens if you try to email mplatten@genmail.net from your Freeserve dialup account right now?
--
simon