This is just a thought...
From what I understand, emails containing formatting are written in HTML. I am assuming that when Access sends the body of the email to Outlook, it sends it as a plain text file. If you embedded formatting using HTML tags, such as 'This is some <B>BOLD</B> text' there is a good chance that it might appear formatted.
I am interested to know if this works. Yell, if you need some assistance with the tags. I dream in HTML, so I am sure I could be of some assistance (assuming that it actually works!!)