In a word, yes.
Several ways of doing it, depending on what version of Exchange is in use, how it has been configured and how good the backup regime is.
Also if a 3rd party archiving system is in use there's yet more ways of accessing deleted emails.
Your company should have a written policy stating that use of the email system is for work-related purposes, and that all emails are the company's property and can, within reason, be open to inspection by those higher up the food chain (or words to that effect).
SD