I've tried changing numerous settings in Outlook to prevent this switch, and have had with no luck. However, I did find one clue: After opening one of these troublesome emails, I went to the "Other Actions" menu and selected "View in Browser". This opened the email in my default browser (Internet Explorer 8), and my email reply looked just as I had sent it (see screenshot to the left).
I have noticed that when I send out these types of emails where the font appears to switch, when I get a reply from a recipient, I see that not only is the font of the message I had sent still changed, but it also appears changed when I view the email using "View in Browser".
For the record, here is a list of things I have already tried:
- Use message format HTML or RTF.
- Use or don't use theme.
- Change new message and reply default fonts to Verdana or Calibri.
- Use or don't use signature.
- Check or uncheck "Rely on CSS for font formatting".
- Check or uncheck "Save smart tags in e-mail".