Your mailbox should give you options as to that sort of thing. If you've deleted or trashed e-mails, you should have a folder that says "trash" that contains all the e-mails you've deleted over a certain period of time. That folder will only hold those e-mails for a certain number of days though.
Sent items = same deal. There's a folder that should take you to view all of the e-mails you've sent.