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

Posted on 2004-10-25
Last Modified: 2013-11-16
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.
Question by:gsxrblur
    LVL 51

    Accepted Solution

    you need at least TCP smtp (25) and UDP dns (53) in both directions (sorry no Checkpoint handy for copy&paste rules)

    Author Comment

    Thanks, I think i have the problem fixed.

    Write Comment

    Please enter a first name

    Please enter a last name

    We will never share this with anyone.

    Featured Post

    Looking for New Ways to Advertise?

    Engage with tech pros in our community with native advertising, as a Vendor Expert, and more.

    To setup a SonicWALL for policy based routing to be used with the Websense Content Gateway there are several steps that need to be completed. Below is a rough guide for accomplishing this. One thing of note is this guide is intended to assist in the…
    This article offers some helpful and general tips for safe browsing and online shopping. It offers simple and manageable procedures that help to ensure the safety of one's personal information and the security of any devices.
    This video Micro Tutorial is the second in a two-part series that shows how to create and use custom scanning profiles in Nuance's PaperPort 14.5 ( But the ability to create custom scanning profiles a…
    Sending a Secure fax is easy with eFax Corporate ( First, Just open a new email message.  In the To field, type your recipient's fax number You can even send a secure international fax — just include t…

    846 members asked questions and received personalized solutions in the past 7 days.

    Join the community of 500,000 technology professionals and ask your questions.

    Join & Ask a Question

    Need Help in Real-Time?

    Connect with top rated Experts

    9 Experts available now in Live!

    Get 1:1 Help Now