You send a mail to HOST.com, but you receive the NDR. Can you send mails to other outside domain?
Or you just receive NDR from HOST.com?
If yes, seems like there is some configuration issues with HOST.COM domain.
For example, HOST.COM is not set as authoritative domain.
Could you please also make a telnet test to HOST.com?
How to Use Telnet to Test SMTP Communication
- Proposed as answer by Frank.Wang Friday, February 12, 2010 1:52 AM
I configured the new DNS servers changed the namservers every thing is working fine just Exchange is creating issue. We have two Namservers. Some time emails are delivered and able to receive replies but sometimes they are rejecetd.
Telnet is working fine on all ports. Same time updated the Juniperfirewall Antispam and Antivirus subscription but able to send by official id, gmail, hotmail and yahoo why not able to send and receive fom particular domain.