vim/ftplugin/mail.vim

   1 setlocal formatoptions+=awt " auto-format
   2
   3 " pad '>' with a single space
   4 keeppatterns keepjumps %s/>\ze\([^> ]\|$\)/> /e
   5 " remove spaces between '>'
   6 keeppatterns keepjumps %s/> >/>>/ge
   7 " remove trailing spaces in header
   8 keeppatterns keepjumps 1;/^$/s/ *$//e