Strange Problem with Email after migration

Hi Guys,
Thanks for the support on this, I have been wrecking my head about it all day.

I have now removed the second MX record as it would seem it has nothing to do with their actual exchange server.

intends does seem to be a lot happier today however they are still experiencing the same issues in that they can't receive or send mail from hotmail and they can't receive mail from bnlproductions.co.uk but yet they can send mail to this domain.

I did get an error report this morning from them saying that some users were not recognized and they thought it was our fault however I explained that all we do is redirect their mail, we don't actually host it for them.

I have contacted the company thats hosts their mail and explained the problems and their engineer is looking into it.

I honestly can't see any problems with the DNS settings, from what I can see it should work perfectly but its not for some reason.

Any other suggestions would be greatly appreciated.
 
I think they have 7 users in total. We actually dont host their mail, this is done by another company so I can get access to the exchange server itself to diagnose any problems.

If it was up to me I would be simply hosting it on our server but I dont believe this is an option unfortunately.
 
So after some further testing, I have found that a small amount of users on the bnlproductions.co.uk domain can email some users on the niyf domain but not all.

Would SPF records and/or domain keys have an effect on this?
 
So, let's get this straight, the domain niyf.org has an MX record, that points to an Exchange server you don't run, and some senders from bnlproductions.co.uk can't email some recipients on niyf.org?

I would try to establish how consistent this is, is it always the same senders/recipients that have problems.

I would also check Message Tracking logs to confirm if emails were actually delivered or not, the sender should be able to track from their end if they are running Exchange or similar.

Also check message queues, if they can't be delivered, are they queuing up? Are there errors being generated on the queues?
 
Eulogy, you have got it right with the top comment.

Consistency is with certain users in-fact only one can send and receive from their bnlproductions account.

The messages are not queuing on our side.
 
Sending and Receiving are two totally unrelated operations, it's perfectly possible to have [email protected] be able to email [email protected], but NOT the other way around, it's unlikely for the same problem to be causing two way mail flow communication failure.

I would suggest getting the people who can't send to your domain, to check for:

1. Bounce Backs, if you can post one here we could take a look.
2. Message Tracking Logs from their servers, where are the messages going? errors etc.
3. If you are on good terms with the other sides IT support, get them to see if they can telnet to your MX record DNS or IP address on Port 25, if not it could be getting blocked by Firewall or similar. If they can get there on IP but the DNS name resolution fails, they can investigate that further.

You can't do much without having a confirmation that mail was actually send to you.

Likewise, if the senders on your domain can't email the other domain, they can also check for NDR's and check the tracking logs on the Exchange server for confirmation of delivery (or not).

Someone mentioned about SPF records, yes these can help you to deliver emails to some recipients, but generally if an SPF lookup fails an NDR would be generated to advise you of that. No one wants emails to "black hole", or go into the abyss, if no NDR is being generated then in my experience it's being delivered "somewhere".

Typically find this is down to misconfiguration of DNS or a Mail system is accepting mail for a domain it should not.
 
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