I've recently noticed what may be a new spamming technique: sending mail to Yahoo Groups with an invalid group name - since Yahoo! doesnt! seem! to! use! SPF, this intentional backscatter gets delivered to the forged recipient address with the payload in the returned message text.
There are two ways of recognising it: - the List-id: header is set to <UnknownList.yahoogroups.com> - the user part of the To address is alphanumeric soup Martin
