Usually it is reply all to a "reports of Exec X" mailing list which are autogenerated and in Cisco not set to disallow replies even if the number exceeds X. Once in a blue moon, after a major incident (like this one) IT goes around and sets all of them to moderated or no-reply, however the generation is untouched. So when you have a major reorg (like now) you get a set of new lists/execs which are no longer filtered.
I always find it amusing when people reply all to that with "unsubscribe" to these too.
Yeah, sure, go into the HR self service portal, find the link which says resignation and fill it in.
Anon for obvious reasons.