The best way to test a policy is to perfrom the drop test as defined in TECH219668.

The Drop test can test a policy without actual network traffic. 

To perform the drop test you must use an .EML file.  .EML files are created with Outlook Express.

Outlook Express is not very common these days.

So you can use the following workaround for testing content based detection.
 

Use Notepad or a text editor and follow the following format of a .eml message.

From: "Mr Vontu" <[email protected]>
To: "[email protected]"
Subject: testing keyword policy
Date: Wed, 18 Jul 2012 15:00:00 -0000
MIME-Version: 1.0
Content-Type: text/plain;
        format=flowed;
        charset="iso-8859-1";
        reply-type=original
Content-Transfer-Encoding: 7bit
X-Priority: 3
X-MSMail-Priority: Normal
X-Unsent: 1
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.3790.4913

testvontutest

Then save the file as a .eml 

Once you have the .eml file you can copy / paste it into the \Drop folder on a Network Monitor.