Configuring preferences and options in Outlook.com
I have the same problem with font sizes changing at will - tried all the suggestions I found on various forums regarding the problem - if your product team is working on this, they're not working very hard, are they.
It is now November 2014, the ridiculous problem with the font size persists and although this will be a schlepp, I have no other choice and will change to Gmail or some such. Because it is SO EMBARRASSING when you send an email which looks like it's been written by a 2-year old playing around with font-sizes.
On the upside: I thought pathetic, service delivery was unique to Africa (where I live). It pleases me to know that this is not the case.