Is blocking e-mail by means of the keywords in the From field useless?
No, this is quite useful for blocking undesirable people rather than spammers. Blocking keyword in the ‘From’ allows you to block by partial e-mail address. Whatever is entered here will block an e-mail item if a match is made anywhere in the e-mail address. This feature will also allow you to block entire domain names (i.e. @unwantedmail.net).