Mail is sending my legitimate emails without a sender.  This happens ONLY on my iMac (running Mavericks).  When I send from my MB Air, the mail goes out with a sender; when sent from my iPhone, mail goes out with a sender.  When I send from the same account but on my iMac, it goes out with no sender.
HELP!
	
		
			
		
		
	
				
			HELP!