You can't actually "pull back" a sent email, but if you look in Mail's "Sent" folder, you should see your sent mail there, from which you can copy the text, subject line, and recipients, paste into a new mail message, edit, and resend.
Even in Outlook the ability to retrieve a sent email is dependent on the Exchange server rules. If you are not using Exchange or if there is no sent mail holding rule, then once an email is sent, it is gone!