Which ports to open on firewall for Exchange 2003- The connection was dropped due to an SMTP protocol event sink.

My problem is with outgoing mail on. I have a checkpoint firewall appliance that I have my new Exchange server behind. When I make the server an exposed host everything works fine.  When I bring it behind the firewall outgoing mail does not work as it should.  on the firewall I have made use of mapping of my external IP address to the internal IP address of the server. I have 2 rules : ALLOW pop3 and ALLOW smtp.  On the servers tab in my checkpoint firewall I have also checked the boxes for SMTP and POP3 and placed the proper IP address there.  I don't have any DNS servers listed in the SMTP virtual server in System manager. Shoudl there be a DNS port opened on the firewall?  How come emails are not going outbound unless I make my server an exposed host (no firewall).

I am getting these queue errors:

The connection was dropped due to an SMTP protocol event sink.

The Connection was dropped by the remote host.

An SMTP protocol error occurred.

Unable to bind to the destination server in DNS

The remote server did not respond to a connection attempt.
gsxrblurAsked:
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ahoffmannCommented:
you need at least TCP smtp (25) and UDP dns (53) in both directions (sorry no Checkpoint handy for copy&paste rules)
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gsxrblurAuthor Commented:
Thanks, I think i have the problem fixed.
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