Hi, I´m sorry for my english, but i hope you can understand.
I work a a small company, that has 3 servers, 2 DC (one windows 2000 and the other windows 2003) and one Mail server with Exchange 2003 (on top of windows 2003 R2).
We had only one domain registered, domainA.com, but then my boss wanted to have two domains domainA and domainB. We had to change the mail server, so we transfered the mailboxs to another server and configured it to receive from the two domains. We asked our ISP to create one mx record of the domainB equal to the older domainA.
Now we receive mail from the two domains (ex. usara receives mail from usara@domainA.com and usara@domainB.com), but only send from the new domain (domainB).
The problem is that after these changes in our network, we noticided that a few domains could receive our mails but could not send back (reply or new message), but could send to the older domainB.
The message that these domains receive is this:
usara@domainB.com on Mon, 26 Jun 2006 12:25:41 +0100
The e-mail account does not exist at the organization this message was sent to. Check the e-mail address, or contact the recipient directly to find out the correct address.
Aparently this is a NDR not sent from our server, but from our ISP.
This only occurs in 3 or 4 from 100 domain that we receive and send mails...
I tried a few tips that i have found here, but in vain... i don´t have the skills to resolve this problem alone.
Please help me and again sorry for my lousy english.