Remember that we're in the Microsoft era. I just checked -- Netscape 4.0+ will filter on body, but not arbitrary headers -- it's subject/sender/body/priority/date/status/to/CC/to or CC/age in days or nothing. Outlook and its derivatives are similar. Since these account for a huge fraction (I'd estimate over 75%) of the clients being used by people today, the problem being solved by the recipe is a real one.
Charlie Summers wrote:
Again, since anyone with a reasonable client (ok, so Mail can't do this automatically...know anyone who uses Mail as their main email client?) can filter on just about _anything_ (I'm using an old 3.1 version of Eudora, and it can filter on the _body_ for goodness sake, let alone every conceivable header field!), why do we need to pander to people too lazy to spend a few moments reading the manual or help file that came with their software?