You can enable case-sensitive filtering for all your keyword filter lists. Case-sensitive keyword filtering is disabled by default (that is, keyword filtering is not case-sensitive).
To globally enable case-sensitive keyword filtering-
In the Forefront Protection 2010 for Exchange Server Administrator Console, click Policy Management, and then under the Filters section, click Filter Options.
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In the Filters - Filter Options pane, in the Transport Filtering Options section, select the Enable case-sensitive keyword filtering check box, and then click Save.