I've been party to a few investigations in my time that involved trawling through thousands and thousands of emails. Those investigations generally involved fraud and misconduct. I have looked at the contents of a lot of mailboxes, and spent way, way too many hours reading emails from some very sad and useless people.
The one common thread though amongst all the mailboxes and mail traffic that I looked at was that almost every mailbox was littered with joke emails. Some were crammed full of them, making me think that the only thing those people did all day at work was to read funny emails. The dead giveaway of course when opening up a suspect mailbox was a folder marked "jokes", which might contain thousands of emails that, frankly, after five minutes, were boring as batshit.
My assumption is that the poor bastards that hacked into the University of East Anglia CRU computer system must have spent weeks afterwards filtering out all the jokes before publishing this rather startling set of emails and documents.