HTML Emails Not Using Default Font

[srm]

I'm using O2003. I have all my fonts composing, reading,
replying/forwarding to be Tahoma 10. Sometimes when I get a message
and reply, it defaults to Times New Roman 10. I then need to change it
back to Tahoma.

Can I change this so it always defaults to Tahoma 10 all the time. In
the past I didn't think this could be done, but wanted to ask if maybe
it was now possible.

Thank you.

Shawn