Same thing happened at my company (~40k employees) about 2 years ago. Fortunately it is split across a couple of timezones, but after about 300 'Please do not

Same thing happened at my company (~40k employees) about 2 years ago. Fortunately it is split across a couple of timezones, but after about 300 'Please do not reply-to-all' replies-to-all, apparently the exchange server crashed and took care of the problem :P