Apologies if this is answered elsewhere – after years of using SpamSieve I’ve not had reason to come here for advice.
A clueless individual sent me and 50 other individuals an email where my and their addresses were fully exposed in the cc: list. Yes, so now I have 50 clueless co-respondents replying all. Repeatedly. This group of people is nothing that i care about, so I would like to find a way to mass-blacklist the whole crew.
Sorry, there’s no built-in way to do this. You could modify this script, which adds blocklist rules for a message’s sender, to instead add rules for the recipients. However, it’s not ideal to tell SpamSieve that unwanted but non-spam messages are spam.