If you click SPAM it should send any future emails from that address directly into the trash. You can delete your trash every so often or it will probably do so automatically. At least mine never has more than about 10 -15 things in it and then they disappear.
Jan in Chatsworth
From: Char Holte <firstname.lastname@example.org>
Sent: Wednesday, August 3, 2011 1:30 AM
Subject: [iris-photos] RE: OT blocking unwanted emails
Does anyone know how to block an unwanted email?