If you use the patched mmime to generate format=flowed emails, the
following code added to ~/.vimrc will give you a quick visual check that
the trailing whitespace is in the right place. Adjust the last two
autocommands if you configured a different maildir for drafts of outgoing
messages.
function! FixIndented()
" remove spaces at end of indented lines
silent! %s/^\s.*\zs \+$//
endfunction
function! TextFlowed()
setl tw=72
setl fo+=w
setl nojs
setl nosmartindent
setl list
set listchars=trail:•
endfunction
autocmd BufRead,BufNewFile */sent/cur/* call TextFlowed()
autocmd BufRead,BufWritePre */sent/cur/* call FixIndented()