Hi,I always get this error message when sending to specific domain:"An error occurred while trying to deliver this message to the recipient's e-mail address. Microsoft Exchange will not try to redeliver this message for you. Please try resending this message, or provide the following diagnostic text to your system administrator.The following organization rejected your message: mail.domainnamehere.com"I have confirmed with the recipient that they have received the email though. I also sometimes get this error on other domains and they do not receive my email:This message has not yet been delivered. Microsoft Exchange will continueto try delivering the message on your behalf.I have confirmed that 3rd party email can send out fine except mine(Using exchange). The recipient however can send email to me. This problem started when we had an Exchange 2003-2007 Migration.What I have done so far is:1. Change the firewall settings to point to the new exchange server. 2. Update DNS records, create reverse DNS lookup.3. Deleted the N2k file and tested using webmail - still the same. Only a few domains are affected from what I know so far, but I can't figure out why we cannot send out to some domains. This all started after the migration. Any feedback would be appreciated.Thanks!

Just for testing , creates a seperate send connector for that domain and see if this still goes on. This doesnt make any sense still give it a shot and post the results here.Raj

HiOther suggestions for you.1. If you change some IP address, please check your new IP address is not contained in the blacklist by RBL or other third party blacklist.2. Please confirm the receipt party whether has a gateway for mail system, you culd let them to add your domain into the whitelist.3. Please confirm your server could do the MX lookup for the domains, somtimes caused by DNS not updated at ISP where looking up at or DNS not flushed4. Are there other sofware install on the other side exchane server, such as forefront for exchange, maybe some rules caused that.5. You could check the message tracking log to get more detail information about it.Regards!gavin

some mail servers request explicit to start the conversation for HELO not EHLO test for it

Hello everyone,I managed to "fix" it by using external DNS lookup on my send connector. So far, those messages(around 5 domains) are no longer giving me NDR. I'll continue to monitor this and see if I still get any problems. @Gavin- The external IP address that im using is the same as my old exchange server.- The DNS is also updated by my ISP.- No other security appliances/software installed aside from firewall.