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SMTP Server: Can not send mail to one domain

Posted on 2014-09-03
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Last Modified: 2014-09-05
Has 3 different IP'sHi
We have a mail server and trying to send mail to receipient in Zimbabwe
For the last few days they can not receive mail from us but can from others.
Thats why they thing the fault is with our server

I have made a MX Lookup on their domain. Please see attached

I then checked our logfiles:
Some days ago we send and their received. Our SMTP Server used their SMTP IP: 197.211.205.130
We can send and they can receive

Now today I try to send again but it now goes to their  IP: smtp:217.74.224.110
This fails

I have made some lookups on the 2 SMTP Servers and on mxtoolbox the last one gets time out.

My First Question:
My Conclusion is therefore that its their problem.
Is this right?

My Second Question:
How can it be that our SMTP Server one day uses one of their IP and the next day a different?
I guess this is outside our power as we do not have our own DNS Server but uses our ISP's DNS Server


Can anyone comment on this please so I can forward the right conclusion to them
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Question by:morten444
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Expert Comment

by:Hypercat (Deb)
ID: 40303740
I just did a DNS check (through DNSStuff) on their domain.  The only MX server IP address that is responding is 197.211.205.130.  The problem may be at their end in that it may be a DNS issue that is caused by a change in their DNS records that hasn't been disseminated through the Internet. Something is causing you to pick up the 217.74.224.110 address and that server isn't responding. However, I would try clearing your DNS cache on your internal DNS server, which will cause it to do a lookup again at your ISP's server and see if that sets your cached record back to the 197 address.  

If that doesn't work, remove your ISP's server from your DNS forwarders tab (assuming that's how you have it set up) so that you're using only the root servers for DNS lookups. It may be that your ISP's server is caching the wrong IP for some reason and you're getting it from them. Then clear the cache again and retry.
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Accepted Solution

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footech earned 500 total points
ID: 40304867
By way of workaround, it's also possible to configure your mail server to route mail destined for their domain to a particular server, rather than relying on MX records.  However, this would mean you would have to update your server if their info ever changes.  So for example, you could route all mail to the chembada.co.zw domain to mail2.chembada.co.zw.

As all three records are returned by an MX lookup for their domain, unless one of those hosts isn't responding at all, then then it's possible for all of them to receive mail.  Even for sources that respect the priority of the MX record, and tries to use mail2.chembada.co.zw and mx3.chembada.co.zw first, unless one of them isn't responding at all, the sending server can try to use either one.
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Author Closing Comment

by:morten444
ID: 40305839
Thanks for Answers
It seems like Imail.8.2 can not relay from one that does not respond to one that does.
So as a temporary solution i added the working record in servers host file and now it works. Must be because its quite old software

We have a zimbra server in test lap and that does relay from one that does not responding to one that does.
So the solution is to move them over as they do occationally have issues with one of the lines

Thanks for input
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