I have set up a mail server using the zcs-4.0.1_GA (Open Source) version on a RHEL 4 box with 1GB RAM.
Initially, I did encounter some problems but that was solved by searching the forums. Now the setup is running perfectly and I can send and receive mails from the Internet without any issues.

The domain for which the Zimbra Server was setup is first.site.com.

There are two other domains namely 'site.com' and 'second.site.com' which are handled by other administrators and running separate mail servers(not Zimbra).

I am responsible for the 'first.site.com' domain only.

Now, I wish to send mails to the two 'local' domains namely site.com and second.site.com directly to a mail server with IP address without using any DNS servers for these two domains.

Is there some way by which I can specify Zimbra to send the mails to for the above two domains only, whereas performing regular DNS lookups for all the other domains?

I tried to search the forums but could not find a solution to the problem. Any help would be appreciated.

Thanks in advance.