I sometimes wish to find emails that I couldn't have known I would need again.
Right now, I've been looking for the email address of the landlord of the house I lived in until 2009. I'm happy that I didn't remove his email saying that his son would come on Friday to fix the door handle.
Right now, on my main mail, I have ~400 mails in Trash, but only 10 in Inbox and Archive + another dozen in Sent.