Exchange

From: David MacKay (anonymous_at_discussions.microsoft.com)
Date: 04/25/04 

Date: Sun, 25 Apr 2004 02:16:03 -0700

Hi,

I run an Exchange server for my small business, my ISP is NTL via a 600K cable modem and my hosting company is Zen. My problem is some mail deliveries are becoming difficult from a dynamic IP, that didn't used to be a problem when I was on Zen and ADSL with a fixed IP. Notable examples are AOL, which will not collect from an SMTP server on dynamic IP. To get round this I set a new SMTP connector in Exchange to route all mail for the domain AOL.com via the NTL mail server, this works OK. However I have just come across one that will not, whenever I send mail I get the following back:

Your message did not reach some or all of the intended recipients.

      Subject: Valve
      Sent: 22/4/2004 08:28

The following recipient(s) could not be reached:

      info@teqcom.com on 24/4/2004 02:01
            The e-mail account does not exist at the organization this message was sent to. Check the e-mail address, or contact the recipient directly to find out the correct address.
            < mta1-win.server.ntlworld.com #5.1.1 smtp; 550-mta01-svc.ntlworld.com [62.253.***.***] is currently not permitted to relay 550-through this server. Perhaps you have not logged into the pop/imap server 550-in the last 30 minutes or do not have SMTP Authentication turned on in your 550 email client.

What I think is happening is that this server is doing a reverse DNS lookup on the domain from which the return address is listed (Me@MyZenHostedDomain.co.uk) and getting a different answer than the NTL server that is sending the mail. I cant think of a way round this, I have tried asking Zen to let me send via their SMTP server from an NTL connection, but no dice! I could either swap Zen as the domain host or go back to them for ADSL, but both involve hassle. Any other ideas? Also is there a decent way of finding out what Exchange is doing when it sends these messages?

Cheers, Dave