Your host name and IP address doesn't match in Exchange 2003

I have encountered a problem that a company refuse to accept our emails because our host name and the client's resolved name is different. Our Exchange server is go directly out the internet with NAT. Could I change the outgoing DNS name of my Exchange using the SMTP Virtual Server -> Delivery -> Advanced -> Full qualified domain name.

My client is using Exchange RPC (RPC over http) to synchronzie the local mailbox rather than using the POP3 and SMTP to send or receive the email. Do this setting help or not ?

Message return by the client is :
 <xxxxx.YYYYYYYYY #5.7.1 smtp;554 5.7.1 1111.2222.3333.4444 Message refused. Your host name(xxxxx.ZZZZZZ) dosen't match with your IP address>
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Jejin JosephCloud Evangelist Commented:
It might be that this company is doing a Reverse DNS Lookup. Do you have a PTR record in place which resolves the external IP Address of your mails server to the host name of the mail server ?
This looks like a classic DNS mismatch.

Either your reverse DNS doesn't match what the server is announcing itself as, or the server is announcing itself as an invalid host.

Put the domain name in to and see what it says about what is wrong.
If it is reverse DNS errors then you will need to speak to your ISP.

AXISHKAuthor Commented:
yes, the DNS is registered properly and reserve lookup work fine.

The problem is my Exchange server is using another name which is different from the external one. And not sure whether is I change the "Full qualified domain name", it could help or not ?

Reverse look up from the External Public DNS is having problem. Incase if you have IP's from the ISP then ask them recheck the Host name with IP and reverse lookup also.

Internally When you do Telnet Exchangeserver name @25 it will display a host name. The same thing should be registered externally also.

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