Hemant,
This is happening because your Exchange server is using an internal DNS server, which does not know the MX record for spamfilter.xxxx.net.
I recommend you configure your Exchange server so it routes every out-bound message through Xeams. This is will solve problems:
- It won't have to do an MX lookup. It will blindly forward emails for every non-local domain to Xeams, including spamfilter.xxxxx.net
- Xeams will learn from what is going out and will give credit to outside users when they reply. Check http://xeams.com/FilterOutBound.htm for details. When you configure this, remember to:
- Add your Exchange server's IP to allow relaying
- Add your Exchange server's IP among trusted IP,
- White list the IP address for your Exchange
