Hello all,
I'm using a suse 10.0 linux server with postfix installed, i have seperate domain and dns servers installed (windows 2003), this dns has forward lookup zone configured, Linux postfix server is configured with the relayserver which is outside my domain.
All of sudden my mails for out side my domain are not going thru, i'm unable to do a telnet to port 25 to the relayserver, I found out from log that it is giving the error unable to resolve my relayserver.
I bit confused can't think where to pin point the error.
anybody help...?

Do not mark messages as urgent. We volunteer our time to help folks, and this isn't a rush for anyone but you.

The signs point to your relay server being down. Is it? What have you checked so far? Either restart the server, or restart the postfix service on it.

I have restarted the postfix services but the problem is still there...

Need more info to work with other than 'it's not working' 'I can't connect to it' the 'can't resolve hostname' error is useful, but you need to follow up on it with basic troubleshooting steps..

Did you log into the mail server and test DNS resolution ? dig mail.relayserver.com

Did you verify the correct dns servers are in /etc/resolv.conf ?

Did you check the posfix configuration for errors ? postfix check
Last time I had a DNS issue on my mail server, postfix check revealed to me that the DNS servers listed in the chroot for postfix, did not match the correct working DNS server entries in /etc/resolv.conf

Have you run through the basic diagnostics ? http://www.postfix-book.com/debugging.html

This was working previously, correct ? What if anything on the mail server or network was changed before it quit working ?