DNS errors in mail delivery

I have used the same Exchange server for over 2 years.  I have one server that delivers approximately 800 emails per day to me.  With all of these emails, it is imperative they be delivered.  
Approximately 2 months ago, I started using a new mail host.  I moved my MX records to the new server.
Ever since that time, 1/2 of my mail goes to the new server, 1/2 to the old.  I have kept the old server up in case something like this happened.  But after a month, shouldn't it have ceased?
Am I hurting the situation by leaving the previous path open?  
If I have the new server reject all incoming mail, will the delivering server go peek at the MX record and see that it is changed?  Could I have missed something BIG?

Thanks.
TIgerVAsked:
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mds-cosCommented:
OK, some things to check:

1)  Do you have multiple MX records?  If so, you need to have your host delete the MX that points to the old server.

2)  Did your old hosting company keep your domain records in their DNS?  If so, you need to have them remove you (but this would not account for half of your e-mail...only people using that host would be affected).

3)  Do you have a network device in place that is sending e-mail to the old server?  For example, if you are load-balancing firewalls and one has a NAT pointing to the new server but the other still has NAT pointing to the old server.


I also want you to go to www.internic.com and do a whois lookup on your domain.  Make sure that DNS servers listed there are pointing to your new hosting company.
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rgc6789Commented:
Make sure you have all the email boxes on the new one. Usually, when incoming emails come in, the sending email server will check the first server on the list for a particular email address and if it doesn't find the address, it will try the second one. Could this be the case with your issue or are they coming in 1/2 and 1/2 per mailbox?
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evan021702Commented:
It should only take about 48 hours for the DNS records to propogate.  If all MX records are correct, then you need to also make sure your internal DNS cache is cleared and that your router is forwarding POP/SMTP to the correct IP address.  
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TIgerVAuthor Commented:
Actually, wouldn't it be the Sending end's DNS cache?  The records are propogated, but it seems that one or more of the servers sending (all the same domain) is cacheing the old address.  BMTGRAD.COM is the domain.
When I look at the MX, I see presmtp.ex1.secureserver.net, which is the newest.  
My concern is if it hits the old primary server and they reject the mail, will the sending server automagically check the dns again?  It should have done so already, it's been greater than 30 days.  I can't afford to lose any mail.


TV
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evan021702Commented:
Yes you are correct, however whenever I make a major change I always like to be sure my servers have up to date information.  
I had a similar problem when a clients ISP's DNS servers were over taxed.  The DNS requests were not being serviced timely so the clients servers were using their cache.  If this is the only domain giving you issues, I would contact the administrator of that domain to check their DNS.
How is your email network setup?  Do you have two different external IP addresses serving the servers?  If so why not add the old servers IP address to the new server as a secondary?  That way if it is resolving to the wrong address it will still go to the correct server.
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TIgerVAuthor Commented:
Unfortunately, the sending server belongs to the government.  Nobody there that can help, since they won't talk about their DNS setup.  :-D
Their helpdesk says "DNS?"  and they won't forward you to the tech controller who knows.

Given that, I am correct in thinking that shutting off all service for my domain on the old server SHOULD permit all mail to go through to my new one? (Had to ask one more time for good luck)
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rgc6789Commented:
It looks like you have both mail servers set as primary which is probably your problem. Both bmtgrad.com.s8a1.psmtp.COM and presmtp.ex1.secureserver.net are set to primary. Set your old one to secondary and that should take care of it.

Also, there is a third mx record for bmtgrad.com.s8b1.psmtp.COM, which is probably a backup.
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evan021702Commented:
How funny!  
What I would do is add the IP of the old server as a secondary on the new server, shut off the old system for a while and see if you receive emails from the problem domain.
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mds-cosCommented:
I agree with evan.  Contact the admin of that specific domain -- the problem is on their end if you checked your MX records and only your new server shows up there.  If you are running your own DNS you need to be sure that all of your DNS servers are up to date (ran into a problem once where one of our DNS servers quit accepting updates).  If not, you should be able to have your hosting company verify that their DNS servers are all updated.

Keep in mind my step 2 above though.  Is it possible that BMTGRAD.COM is using the same old host that you were using, and the old host did not clear out their DNS (this is assuming that you moved your DNS servers, not just updated your MX records...if that is not the case ignore this).

If you shut down your old sever, the domain in question might just start generating NDR's to it's users.  If everything is right on your end, you know there is something wrong on theirs.  Making the assumption that their server will "requery" would not be a good one.
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mds-cosCommented:
Why set the old MX record to secondary?  Just delete it since the server is decommissioned.  And if the other MX record is not a backup, delete it too.  You should only have active MX records for active mail servers.
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TIgerVAuthor Commented:
I went back to my DNS, and I only show one MX record.  That is on secureserver.net

Any idea where the 2nd could be coming from?
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mds-cosCommented:
Would you make it easy for us to do a quick DNS digg and let us know what all of your e-mail domains are?  Thx.
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TIgerVAuthor Commented:
I am only concerned with bmtgrad.com.  
All mail should go to presmtp.ex1.secureserver.net.

psmtp.net is the old server, turned off now.

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rgc6789Commented:
Ok, now there is only 1 mx record according to DNSStuff.com
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mds-cosCommented:
I dug around a few places, and also come up with a single MX of  presmtp.ex1.secureserver.net...you should be fixed!

You say you are "only concerned with", but does this mean you have other e-mail domains as well?  If you do, and if their MX records are pointing to the old server, and if people are sending to those addresses you will still end up with e-mail coming to the old box.
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