JohnHarvey wrote:
Hmm...I tested that from one account to another and the font and size reflect as seen in the outgoing email. Am I missing something?
It's not clear exactly how you tested. If you set the Message font in Mail > Preferences > Fonts and Colors to something large and distinctive, and then compose a short message and send it (without setting anything again in the new message pane), and the do View > Message > Raw Source on the copy in your Sent folder, you should see that the html codes do not mention the font name or size.
In your Sent folder the text will look like the preference settings you made, but because there are no html codes for those in the source, a recipient email app on another machine will not know what they are.