Is it possible to have different font sizes for editing and message actually sent? Recently I switched from Thunderbird and so far really love native Mail.app which is quite lightweight to my surprise!

However the transition seems a bit hard as the size of the font while editing messages is too small for me... Can I have two different font sizes - one for editing and other for actual font size with which messages are sent?

EDIT: My os is 10.6.8, but if you know the solution for 10.7.x, please share it as well :)
The size you set in Mail > Preferences for viewing and composing does not actually have any effect on what is seen at the other end.  To do that you have to select the font for each outgoing individually in the New Message pane (and I think also have it different than the font in Preferences).

Mail's inability to set a default outgoing font annoys many users, who sometimes then switch to Thunderbird or Entourage/Outlook instead.  Also someone did an app here:

http://messagefont.com/