Haha yes i forgot that you may not be using Apples Mail. Lets try the export then file>export, then under the heading "format" click JPG. Then click "scale images no larger then:" in the width field type "800" then the height field should change by itself. Thats what i do for emailing, it's usually the best trade between quality & size, that should be small enough to email. Best wishes JAG
P.S. when you first click "scale images no larger then" what's already in the width height fields? thats your actual photo resolution.