Troubleshooting DNS-related mail delivery problems 2

[kawalker]

My company recently switched ISPs. We have a Windows 2000 PDC, on which our Exchange Server 2000 resides. We, obviously, implemented new public IP addresses and everything was great for a couple of weeks. Then, suddenly, we quit receiving SMTP mail. NOTE: We host our own mail,through Exchange 2000. I had our web hosting vendor change the MX record on our domain (we do not have our own web server)so it would point to our mail server and not theirs. They set up a 3rd-level domain to do this. As I said, all was well for a couple of weeks. What could have happened? No changes had been made on my server. My service pack levels are all up to date. I am able to telnet into port 25 on my ISP's mailserver, from my Exchange server, which would seem to indicate that my Exchange server's DNS is working correctly and that my firewall is not blocking this type of traffic. My SMTP virtual server has stuff sitting in queues, currently. Could it be that a DNS forwarding entry should be on my ISP's mail server?

 

[brontosaurus]

may i ask your domain name?

 

[kawalker]

metcutinc.com

 

[brontosaurus]

dns records look ok. i am having difficulty getting a timely response from mail.metcutinc.com though. is that your ISP's server or your exchange server? can you give me a sample of an NDR from someone attempting to send you mail?

 

[kawalker]

mail.metcutinc.com is our Exchange Server; although, our web hosting service also has mail.metcutinc.com set up on their mailserver, which is why I had them change our MX Record to our new public address for our Exchange Server.
Below, is one of the messages I tried to send from my home email account to one of my accounts (webmaster) here at Metal Cutting Supply.

FROM: &quot;Postmaster&quot; <postmaster@mail.gbronline.com> | Save Address
DATE: Wed, 15 Jan 2003 01:11:04 -0600
TO: <kawalker@gbronline.com>
SUBJECT: Undeliverable Mail


Delivery failed 20 attempts: webmaster@metcutinc.com


Original message follows.

Date: Tue, 14 Jan 2003 15:43:43 -0600
Message-Id: <200301141543.AA2374172982@mail.gbronline.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
From: &quot;Kimberly A. Walker&quot; <kawalker@gbronline.com>
Reply-To: <kawalker@gbronline.com>
X-Sender: <kawalker@gbronline.com>
To: <webmaster@metcutinc.com>
Subject: test
X-Mailer: <IMail v7.13>

test

 

[brontosaurus]

is 199.227.117.126 the correct address? when i telnet to that, the smtp banner is rather odd, definitely not an exchange banner. if it is, we've got to check the server out...

 

[kawalker]

Yes, that is our new public IP address for our Exchange Server. I have the ISP on the line now. Any ideas?

 

[kawalker]

Off the phone, now. They indicated that everything was cool on their end (DNS, re-direct zone file, IP address). So, they're thinking the problem is with my server.

 

[brontosaurus]

yeah, as i said, the dns records looked fine. something is definitely strange with the server, right now it looks like smtp isn't even running (although you may be working on it). how about any routing components in between the server and the internet?

 

[F1lby]

Does your SMTP server have a 'real world IP' or is NAT'd thru a NAT router?
If NAT'd, then the NAT router would route port 25 from the external address to the 'inside' address. Have you changed your servers IP address (if its on an internal network number).
Internal (non internet routable traffic) IP addresses are in the 10.x.x.x , the 192.168.x.x and 172.16.x.x ranges.

This may not help... just a thought.....

 

[kawalker]

It is NAT'd thru a router. We're using a CISCO PIX 506 Hardware Firewall. We did just make a configuration change on that piece of equipment. We added &quot;NO&quot; to the fixup protocol smtp 25 entry, which helped; but, still no mail.

 

[brontosaurus]

well, the smtp banner looks much better now and I'm connecting, but your server seems to feel that it's being hit with invalid addresses when sending the HELO or EHLO command....i'll investigate further.

 

[brontosaurus]

i sent a test mail from a hotmail account to your webmaster. let me know if it gets there...or I'll let you know if it bounces.

 

[kawalker]

Got it! We made one other change on the SMTP virtual server. On the Access tab (from Properties), under Authentication, we clicked the box that allowed Anonymous Access. The only things that were checked there previously were Basic Authentication and Integrated Windows Authentication. Now it works. I still don't know why it quit working; but, that's moot, I suppose.

Thank you for your time and assistance.

 

[brontosaurus]

Yup, got your replies. Great work and have a good weekend.

 

[F1lby]

Ah-ha.
If ur smtp server was set to 'Require Authentication', then it would require a valid username and password for another smtp server to fire mail into it (this seems to be a Microsoft 'special' and would not normally be required except for site to site smtp servers that shouldn't receive mail from other sources, but your server is set to receive mail from unknown hosts, so anonmous auth is the way to go).
Anyway, good news u r working ok