Bill,

I have a customer that can't send e-mails to two of his suppliers in China in that his e-mails keep bouncing back with a '452 Invalid sender' messages.

Not spcifically so stated, but shall we presume that these come from your mail server, and that it is an Exim MTA you are running?

If so - are you supporting what the destination needs if it does a sender verify callout?

(extended logging should show at least a connection from them shortly after your message hits the remote_smtp delivery phase).

Call that possibility ONE.

Ah, you may have something there. I don't know if the firewall that was set up by people from Pintar's head office has opened up port 113 for the ident server. I will check.

I tried sending an email to the postmaster there and it bounced back with:

<[EMAIL PROTECTED]>:
218.30.103.130 failed after I sent the message.
Remote host said: 552 This user's disk quota exceeded, anyway you can send a smail (<1KB) message to inform the person.
The email was way less than 1K.


Different issue - not related to your problem.

Ok, a red herring.
I tried a telnet to mail.promexsh.com 25 and as soon as I did:

mail from: [EMAIL PROTECTED]

I immediately got the 452 error.


I'll call thei possibility TWO.

pintar.ca resolves to IP 209.250.128.44

but IP 209.250.128.44 resolves to webhost02.pathcom.com

The same telnet from one of my Hong Kong servers, HELO'ing with the hostname in the rDNS, succeeds to the next step:

========

conducive# telnet mail.promexsh.com 25

Trying 218.30.103.130...

Connected to mail.promexsh.com.
Escape character is '^]'.
220-W E L C O M E   T O   H I C H I N A   S M T P   S E R V I C E !
220 mxvip2.hichina.com ESMTP server (quarkmail server - version 1.2.1) ready at Thu, 20 Jul 2006 01:12:27 +0800

helo conducive.org

250 mxvip2.hichina.com Hello conducive.org

^]
telnet>
quit

221 mxvip2.hichina.com Out
Connection closed by foreign host.

========

Perhaps the distant end has an overly strict HELO match rule in place.

What happens if you try to HELO as webhost02.pathcom.com?

I tried that from the pintar.pintar.ca server. It accepted the HELO but when I did the

mail from: [EMAIL PROTECTED]

there was a delay and I got a 452.

This happens as well with the mail.jinmao.com server.


Likewise - it talks to a server with HELO / rDNS match:

========

conducive# telnet mail.jinmao.com 25

Trying 218.244.143.23...

Connected to mail.jinmao.com.
Escape character is '^]'.
220-W E L C O M E   T O   H I C H I N A   S M T P   S E R V I C E !
220 mxdxt3.hichina.com ESMTP server (quarkmail server - version 1.2.1) ready at Thu, 20 Jul 2006 01:14:57 +0800

helo conducive.org

250 mxdxt3.hichina.com Hello conducive.org
^]
telnet>
quit
221 mxdxt3.hichina.com Out
Connection closed by foreign host.

====


On further investigation I see mail.promexsh.com announces itself as mxvip2.hichina.com (218.244.159.32) and mail.jinmao.com announces itself as mxdxt3.hichina.com (218.244.143.23).


smtp banner aside, does your log show the same on actual incoming traffic?
From the above I surmise that hichina.com has some serious problems or am I totally out to lunch (ok, I may be right and still be out to lunch but you know what I mean).

Any constructive advice would be appreciated.


Well - they *may* be more strict about HELO/DNS match on arrival than they are themselves on departure, and/or they use separate servers for incoming and outgoing - not at all uncommon, and not always doen with the best of DNS entries. The banner alone is not conclusive.

But if 'job ONE' is to just get your users' mail to be accepted by them, all you *may* need to do is insure your rDNS and HELO match on your own server.

Easy to try that anyway.


Yes, I agree. I will contact their ISP, pathcom.com and get them to set it up. I was sure it was set up originally when they signed up with them as I always insist that the rDNS be set up that way. I know patchcom.com switched DNS servers a while ago so I bet they forgot the rDNS.

I checked another customer of mine that is with pathcom.com (standardmechanical.com) and a telnet test to mail.promexsh.com passes the 'mail from:' message.

What threw me was the quota exceeded message from postmaster and a post I read on the Neohapsis list about a "452 Too Many" message in response to too many recipients.


I really appreciate the time and effort you put into your response.

Thank you.
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adr:;;14 Halton Court;Markham;ON;L3P 6R3;Canada
email;internet:[EMAIL PROTECTED]
title:President
tel;work:905-471-1691
tel;fax:905-471-3016
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