It is likely that that person did not send the email, but that his or her email address was hacked and stolen. Years ago, people got an email purporting to be from me for one of the scam things - it was not, and I never sent it, but the spammers found and used my email address as the "sender" - did you check the "blah blah blah" text - the full email content? Sometimes it will list the actual machine that sent the mail, and you can see it had nothing to do with the "sender's" email address.