Sender address rejected: Domain not found

I have an order for reinstall email server. I accept the job and finish it in one day ( I use FreeBSD 8.2 release for OS and Postfix for MTA but the longest session during reinstall is backup and migrating mailbox).

Everything seem ok until mail server deployed, local delivery work well except sending to outside. Any email to other email server rejected with ‘domain not found’ message.

I’ve change /etc/resolv.conf to use opendns and google public ip but still not work, the error message still appear and make me little confuse.

After look around finally I got the solution. Its about postfix local resolv.conf file. Postfix has its own resolv.conf file located in /var/spool/postfix/etc.

mail# ls
hosts           localtime       resolv.conf     services

Yes, that resolv.conf file is still holding the value of local dns server I use during installation process.

Change the ip to isp dns server clear my problem and everything seem fine.

Time to set spf record and dkim.

See you.