The Online Family answers:

Email chain letters can clog up your inbox in no time -- and some contain scams or viruses you wouldn't want to forward to friend or foe. First, email your friend a separate note and simply ask her to no longer forward chain-letter emails, jokes, etc. Tell her that your email inbox clogs quickly and that you wouldn't want to accidentally get a virus. But let her know that you'd love to get personal emails from her. If she doesn't stop -- or continues sending emails to everyone in her address book, which includes you -- consider adding her email address to your spam filter. You can still review her emails but this way they'll get automatically filed in your bulk email file. Let her know that you might miss her personal emails because her notes are re-directed to your spam folder now. Maybe this will get her to give up "spamming" her friends altogether.