This error message is seen when you have sent an email and the remote server rejects the email. In your exchange 2010 or Exchange 2007 queue manger you will see this error. You may notice this error when users cannot send mail only to certain domains but it is fine with others.
This normally means that the address you are trying to send email to, the server is using reverse look ups. This means you send an email from youraddress@yourdomain.com this leaves your system stamped with your IP address. Then when the remote system receives your email it does a check to see if “yourdomain.com” is actually the sender by making sure that the IP the mail came from points to “yourdomain.com”. This is done by querying the PTR record.
So, if you see this error there are two things to check. First is the receive connector that issues the HELO/EHLO to verify the servers identity. This is done here. Make sure you enter the correct FQDN of the server.
Once that is correct, test and if it fails do the following.
At a command prompt type
Nslookup
then we set wat type of record we will query with..
set type=ptr
Then enter your mail domain name.
yourdomainnamenotthistxt
it will then resolve, check that the record it replies with IS YOUR IP address. It will be in reverse.
If there is no record, or the IP address is incorrect then contact your ISP and get them to change the record accordingly.This may take a day or so to replicate , then the mail should flow fine