Mail server cannot send email to a specific domain

[Barry Finkel]

<jr at NoSPAM.jrr> wrote:

>This may not be the place for this and I'm not a DNS pro (although I
>understand the concept and can setup simple DNS entries), but I'm not sure
>if this is DNS related or not, so here goes...
>
>I have a Windows based mail server that has a really tough time forwarding
>emails to a particular domain that is hosted by a hosting company.  The
>receiving domain hosting company assures me there are no problems on their
>end, but I'm not so sure.  I am also unable to forward emails to the hosting
>company themselves.  My mail server SMTP log shows timeouts connecting to
>the receiving mail server.  Every now and then a message will get through.
>Connectivity is not an issue.
>
>I started checking things out and initially found the receiving domain MX
>was referencing a CNAME entry.  They fixed this, but still no go.  Then,
>there was no reverse DNS entry for the receiving MX.  They fixed this too,
>but I have a question about this one.
>
>I'm told by the mail server manufacturer that the reverse DNS entry for the
>receiving domain MX should reference the mail server itself or the exact
>problems I'm seeing can happen.  This is an example of how the reverse DNS
>entries are setup for the subject domain:
>
>Mail server manufacturer says it SHOULD look like this (which is the way I
>usually see them):
>
>x.x.x.x.in-addr.arpa mail.receivingdomain.com.
>
>In the case of the subject domain, the reverse DNS entry looks like this:
>
>x.x.x.x.in-addr.arpa hostingcompanydomain.com.

Due to a world-wide power shortage, all of our crystal balls have lost
power.  If you told us the REAL domains involved, some of us may be
able to diagnose your problem.  Remember that DNS information on a
public server is public information, and there is no need to hide it
from those who could help you.
----------------------------------------------------------------------
Barry S. Finkel
Computing and Instrumentation Solutions Division
Argonne National Laboratory          Phone:    +1 (630) 252-7277
9700 South Cass Avenue               Facsimile:+1 (630) 252-4601
Building 222, Room D209              Internet: BSFinkel at anl.gov
Argonne, IL   60439-4828             IBMMAIL:  I1004994