Use a better email service. For example I use my own domain with all email going to me. Consequently I can use site1@my.domain for one site, site2@my.domain for another. Makes it real easy to see who has been sharing things.

Gmail lets you use plus suffixes, as well as extra dots: http://gmailblog.blogspot.com/2008/03/2-hidden-ways-to-get-m...