07-19-2012 12:33 PM
Please see this KB to see how the built in on-device firewall works:
Unfortunately, it is actually backwards from what you desire. Rather than filtering out a specific email, it will filter everything EXCEPT for (e.g.,) entries in your contact list.
As an alternative, you can investigate the BIS-based filter capability, which may provide you what you desire:
Note that neither of these will do anything about the email arrival at your email server...all either of these will do is block things from coming to your BB.