lets see if i understand what you are trying to do,
you have outlook on windows set to recive and send HTML messages,
on linux you are using the /bin/mail, client to send and recive teh same messages but it only sends as plain text...
in that case i would recomend using a graphical mail client like thunderbird or Kontact (if you use KDE) or evolution( if you use gnome)
it shoudl be there on you system somwhere