Want to protect your cyber security and still get fast solutions? Ask a secure question today.Go Premium

x
  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 7769
  • Last Modified:

501 Domain must resolve - can't find the problem

I am using an Exchange Server 2003.
When sending to some specific servers, I get the error:
There was a SMTP communication problem with the recipient's email server.  Please contact your system administrator.
            <mail.fire-development.com #5.5.0 smtp;501 Domain must resolve>

I don't understand it, because in my opinion I considered everything:
mail.fire-development.com resolves to 78.47.177.236
78.47.177.236 resolves to mail.fire-development.com (RDNS)
There also exists an SPF entry for my domain which is accepted by a great german ISP (1&1).
But still, I get that error for one specific mail server.
When I connect to that server directly via telnet, I say
EHLO mail.fire-development.com
and receive as anser:
Hello mail.fire-development.com (may be forged), pleased to meet you
And after sending the MAIL FROM command, it closes the connection and says "Domain must resolve"

Here is the header of a mail I sent to the big german ISP:
Return-Path: <d.hilgarth@fire-development.com>
Delivery-Date: Fri, 16 Nov 2007 11:41:21 +0100
Received-SPF: pass (mxeu19: domain of fire-development.com designates 78.47.177.236 as permitted sender) client-ip=78.47.177.236; envelope-from=d.hilgarth@fire-development.com; helo=mail.fire-development.com;
Received: from mail.fire-development.com (mail.fire-development.com [78.47.177.236])
      by mx.kundenserver.de (node=mxeu19) with ESMTP (Nemesis)
      id 0ML05c-1IsydS2cL9-0000j4 for d.hilgarth@###.de; Fri, 16 Nov 2007 11:41:20 +0100
Subject: sss
Date: Fri, 16 Nov 2007 11:41:17 +0100
Message-ID: <215C90BFF6C79F4797048B9CB9A991530370EE@win2k3-03.intranet.lan>
MIME-Version: 1.0
Content-Type: multipart/alternative;
      boundary="----_=_NextPart_001_01C8283D.38B11F36"
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
Content-class: urn:content-classes:message
Thread-Topic: sss
X-MimeOLE: Produced By Microsoft Exchange V6.5.7226.0
Thread-Index: AcgoPTfUQ8Jnw860TZG+YXpyuOMqew==
From: "Daniel Hilgarth" <d.hilgarth@fire-development.com>
To: <d.hilgarth@###.de>
Envelope-To: d.hilgarth@###.de

There you can see, that RDNS works, the connection to the mail server comes from the correct IP address and so on...
I don't know what is still missing, please help

0
DHilgarth
Asked:
DHilgarth
2 Solutions
 
Spot_The_CatCommented:
I can't get to a dns server to try this at the moment but - If you do a reverse lookup on 78.47.177.236 does it resolve to mail.fire-development.com?

If it doesn't resolve then that's your problem. You'll need to get the ISP to set a PTR for your mail server in their reverse DNS.

Hope that helps
0
 
SembeeCommented:
Everything looks correct from here. If it is one specific server/ISP then they have a problem - possibly a stale DNS record or something like that. The problem is whether they will talk to you - most ISPs will not unless you are a customer. Certainly you will have problems getting past first line support who will not understand.

Simon.
0
 
DHilgarthAuthor Commented:
@Spot:
Reverse DNS is configured correctly. As I wrote in the question 78.47.177.236 resolves to mail.fire-development.com.

@Sembee:
ok, thanks for the confirmation. Luckily, it is not a big ISP but the mail server of a company we work with and I already contacted the responsible person. I hope he can help me out on this issue.
But what I find strange: If I send my mail from that big german ISP to that specific mail server it gets through...
0

Featured Post

[Webinar] Database Backup and Recovery

Does your company store data on premises, off site, in the cloud, or a combination of these? If you answered “yes”, you need a data backup recovery plan that fits each and every platform. Watch now as as Percona teaches us how to build agile data backup recovery plan.

Tackle projects and never again get stuck behind a technical roadblock.
Join Now