Maybe I'm just lucky.
Right now I have 21 messages in my Inbox, and 27 more in other mailbox folders. That's it; no archive, no personal folders, after 17 years with the same employer.
Once I'm done with the job or task, I copy the information I think I might be able to reuser (say, if I need to do it perform the task again), and the e-mails hit the Delete bin. If I think someone else can use the info, I'll forward them a copy. I'll keep HR requests that involve accessing someone else's account for three to six months.
I'm not keeping anything to settle 'He said, she said' situations. I won't work where I have to feel I have to keep everything to cover my @$$ or where my co-workers are trying to screw me over. Maybe I've gotten lucky in my employers.