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Content filtering rules not working

Created: 13 May 2013 • Updated: 14 May 2013
I want to create a content filtering rule that will prohibit email with MOV attachments to and from outside my organization but allow users internal emails to go through.
I am using Mail Security for Exchange 7 on Exchange 2007. I have SMSE installed on my hub transport server.
I created a rule to quarantine emails with a *.mov attachment and checked the Inbound Messages and Outbound Messages box in the Apply Rule to: section.
My problem is that this blocks internal messages as well. If I uncheck the Inbound Messages box, outboud messages are blocked but inbound messages from external addresses are not.
I thought that by leaving the Internal Messages (store) checkbox unchecked, internal only messages would not be blocked and all others would be?
I attached a screenshot. Thank you.
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