email not reaching another domain

Posted on 2010-01-12
Medium Priority
Last Modified: 2013-11-30
dear all, i have a puzzling problem.
first i will explain my network topoly.i have an exchange server 2003 in my lan.i have an ISA server.behind it there is a hardware firewall.between the ISA and the hardware firewall i have a mail filter server.my users are sendimg mails fine but in the pat week our purchasing department users complained that they are unable to send users to a specific company and they always get this error:
Action: failed
Final-Recipient: rfc822;pissaelkhoury@dhc.com.lb
Diagnostic-Code: smtp;
Status: 5.0.0

i tried to telnet on port 25 the specifeid MX  but no response.
when i talked to them they said that they are reciving normally from other comapnies.
and what is weird is that they can send to us but we cannot send to them.

when i checked the log on the mailfilter i saw a failure message stating that :failed to connect to host (ip) and then the name of the domain.

does anyone has a clue how to solve this. ?thanks
Question by:sparks2000
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LVL 76

Accepted Solution

Alan Hardisty earned 1000 total points
ID: 26295329
Please check your domain against my FAQ which might highlight a problem in your configuration / server setup:
LVL 49

Assisted Solution

Akhater earned 1000 total points
ID: 26295900

first I have to say it is the first time I see someone from my country here :)

second I did a checkup and I can confirm that the issue is not from your side the mail server of the company you are trying to reach is not reachable so nothing you can do about it.

to prove it send an email to them from gmail/hotmail it will bounce back
LVL 49

Expert Comment

ID: 26296007
"when i talked to them they said that they are reciving normally from other comapnies."

sorry i overlooked this part,

I ran a test on their domain at mxtoolbox.com and it gave results completely different than the ones in my nslookup

nslookup is giving 1 MX pointing to mail.dhc.com.lb
mxtoolbox.com is giving 3 mx the first pointing to mx1.cyberia.net.lb

so either they have changed their mail server and DNS didn't finish replicating yet or they have a serious problem of split DNS.

in both cases nothing you can do

Author Comment

ID: 26321025
AKhater,glad to hear from someone from my country also:)
hope you can reach guru:)
thank you for your help and i agree with you that it is their problem .maybe they have blacklisted me .
thanks alahardisty also for your useful tools .they were really helpful.
for that i will split he points :)
thanks again for your support!

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