If you did not permanently delete it (i.e. SHIFT+DELETE) it should be in your deleted items folder.
Hope this helps!
This is true if you are connected to an Exchange Server which holds deleted items for several days according to the policy set for the mail store. However if this is a pst that is a different matter entirely. Please inform us whether this is a mail account using a .pst or if you are connected to an Exchange Server. Including the details of your setup helps us give you the answer you need for your situation. Thanks.