Block Out going E-mail by blocking SMTP Port

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[imrandanish1]

Dear All,
I am using Endian V 2.3
Integrated with "DC" (Microsoft Domain Controller) it is working fine
now I want to block the SMTP port for all the users to restrict the outgoing emails like Yahoo, msn, gmail, aol etc.
i tried the out going firewall by making the rule
Port 25 from Green
To Port 25 on red
but no use please some one help me. 

Is there any way that we can use http filter, Signatures in endian as content filtring