Continuing om with my pet hate, I have been looking at some of the template files shop/mailhive/mailbeez/template name/email/body_html.tpl and a lot of these are not XHTML 1.0 transitional compliant, so I may have my work cut out if I am going to review version 2 for you.
The main culprites that I am seeing is the use of <br> instead of <br /> and <img tags not ending with />.