[brianogilvie]

OK, here's what to do:

In OmniFocus, open Preferences, then Mail preferences. Select the checkbox to "Add Mail Rule to create OmniFocus actions."

Quit Mail and restart. (I don't know whether this is necessary, but it can't hurt.) Open Mail, select Preferences, then Rules. Scroll down to the "Send to OmniFocus" rule.

Select the rule and choose "Duplicate" from the buttons on the right.

Double-click on the new rule. Give it a descriptive name. Where the rule reads "If any of the following conditions are met: Subject begins with...", select Subject in the popup menu and change it to From. Then choose the proper match criterion and enter the address you'd like to generate tasks in the proper field.

If you want the message to remain in your inbox in addition to generating a task, be sure to delete the "Delete message" item in the rule. The key element is that you want your rule to run the script "/Applications/OmniFocus.app/Contents/Resources/MailAction.applescript".