When you want to filter incoming mail with rules, it seems that the only rule you can apply to the From part of the mail is the entire address. This works great if the address is from a specific account, such as *** Email address is removed for privacy *** or *** Email address is removed for privacy ***, but many sites - such as Facebook and Twitter - send notifications that have a consistent domain, but randomized (or literally thousands of possible) account names - per person, for example.