I’ve seen a couple of the conversation-spams described in Misspelled nemesis club: A new twist on spam? It looks like they exploit the typically weak moderation practices of many software discussion mailing lists. Do you think they are human-powered? Are they caught out if you set “default_member_moderation” (new list member postings are moderated) or equivalent in the list software? Google and Yahoo Groups seem to be suffering worst. Do they even have such an option?
I’ve also caught some strange behaviour on one of the SMTP servers we run for a customer. Does anyone know what virus or worm or other nasty authenticates but gives itself away by sending RCPT TO:<MISSING*EMAIL*ADDRESS> to SMTP servers?