I've seen discovery requests. They typically say "responsive documents include, but are not limited to, any and all emails, calender entries, notes, etc, etc. related to Subject X". And then they want a log of everything you exclude with identifying details of the document and the reason it was excluded.

Now, you can sort through all of your employees emails and log all the irrelevant ones and then risk the other side complaining that you withheld something relevant, or you can do a dump of everything and let them sort it out. It's more defensible and a hell of a lot easier to do the latter- remember, you don't get reimbursed for the time it takes responding to the other side's discovery requests.