help with Exchange server (although that's probably not the problem)

[Broheim]

I'm having issues at work with our exchange server; we have a second company within our organization who has their own domainname, all the users are on our domain the only difference is their email adress but ever since they switched DNS provider they only receive a fracton of their emails sent from outside the organization.
Their mail is hosted on our exchangeserver with the emailadress from their own domainname as their primary email in exchange and the automatically generated email adress as their secondary (our domainname). They can receive mail on their secondary adress but not always their primary (so clearly that's where the problem lies).

MX records are configured properly for the domain and when I do a lookup it points to our emailserver just fine.

there are no special rules in the firewall and it just passes smtp traffic along to the email gateway that filters out the spam and malware (none of the mails are getting stopped here) and finaly to the exchange server, as far as I can tell there's nothin in the exchange server that could be responsible for this whole debacle.

if somebody has any pointers on what could be the problem any help would be greatly appreciated

 

[Nothinman]

Are the senders getting bounce-backs or are the emails just disappearing?
Do the message tracking logs show the emails coming into the Exchange server at all?
What about the SPAM appliance?

 

[Broheim]

Are the senders getting bounce-backs or are the emails just disappearing?
Do the message tracking logs show the emails coming into the Exchange server at all?
What about the SPAM appliance?

bounce-backs for the ones that don't get through, no sign of them in the logs, they aren't getting caught in the spam filter.

 

[Nothinman]

Then what does the bounce-back say and where does it say it came from?

 

[Broheim]

Then what does the bounce-back say and where does it say it came from?

This is an automatically generated Delivery Status Notification.

Unable to deliver message to the following recipients, due to being unable to connect successfully to the destination mail server.

can't for the life of me figure out why some make it through and others don't.

 

[Nothinman]

It's possible that the busted sites are using stale DNS records. You say they changed DNS hosts, but did the MX records change during the move too? It would be huge if you could contact an admin from one of the broken sites and get to look at their logs and see what his view of your DNS looks like.

 

[Broheim]

It's possible that the busted sites are using stale DNS records. You say they changed DNS hosts, but did the MX records change during the move too? It would be huge if you could contact an admin from one of the broken sites and get to look at their logs and see what his view of your DNS looks like.

the old and the current MX records are the same and the move apparently happened over a week ago (nobody bothered to tell me until crap stopped working :|), so that shouldn't be a problem, but I might try and see if I can get my hands on the logs from one of the other companies, couldn't hurt (one of them is a company we do a lot of work with so it migh be possible to convince them).

 

[Nothinman]

the old and the current MX records are the same and the move apparently happened over a week ago (nobody bothered to tell me until crap stopped working :|), so that shouldn't be a problem, but I might try and see if I can get my hands on the logs from one of the other companies, couldn't hurt (one of them is a company we do a lot of work with so it migh be possible to convince them).

Unless you can get a bounce-back with more info (e.g. the remote server's actual name), that's your only choice besides blindly changing things and hoping.

 

[Broheim]

Unless you can get a bounce-back with more info (e.g. the remote server's actual name), that's your only choice besides blindly changing things and hoping.

Reporting-MTA: dns;dub0-omc2-s32.dub0.hotmail.com
Received-From-MTA: dns;DUB002-W64
Arrival-Date: Fri, 8 Feb 2013 06:29:27 -0800
Final-Recipient: rfc822;deleted
Action: failed
Status: 4.4.7

this is all I have to go on so far, which isn't a whole lot, this was a test email I sent from my outlook.com account on friday.

the only thing that tells me is that the outlook mail relay never gets a connection to our mailserver, which I already figured out... I think I'll go kick the server racks for a little bit, it always makes me feel better.

the only thing I can really think of at this point is that the DNS is crap, but I've personally used the same DNS provider in the past and they're alright, the admin panel is a little clunky but the service itself has ben rock solid, that was a couple of years ago though.