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 126.96.36.199
188.8.131.52 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
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:
Delivery-Date: Fri, 16 Nov 2007 11:41:21 +0100
Received-SPF: pass (mxeu19: domain of fire-development.com designates 184.108.40.206 as permitted sender) client-ip=220.127.116.11; firstname.lastname@example.org; helo=mail.fire-development.com;
Received: from mail.fire-development.com (mail.fire-development.com [18.104.22.168])
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
Date: Fri, 16 Nov 2007 11:41:17 +0100
X-MimeOLE: Produced By Microsoft Exchange V6.5.7226.0
From: "Daniel Hilgarth" <email@example.com>
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