Re: Bad Solution
Occasionally, it's a message that is of use to most of the company, or at least comes from a high-enough level that you can't just fire them. Instead, inflict that punishment on anyone who responded to the address with something pointless. The punishments go as follows:
Person who sent out original email and didn't block reply all: Warning on first offense. Loss of send-to-more-than-three privilege on second one.
Person who first sent a message on reply all with some related query (or people if multiple sent at same time): Presume they didn't check the headers. No action.
Person who sent related message to all after having received other people's messages on the thread: Warning on first offense. Similar loss of privileges as thread origin if the problem continues.
Person who sends unrelated email, not knowing reply all is in effect: Various penalties depending on how merciful you want to be.
Person who sends unrelated email, knowing that reply all is in effect: Fire them immediately, but not just by having their manager inform them. I suggest having security chase them out of the building and posting video of it on the intranet. We all need some distraction, but on our own terms. I'm guessing that watching that person get chased out of the building will be more entertaining than whatever email they sent.
Biting the hand that feeds IT
