Saves messing about with Return-Path for qmail and it works with Exim too.
message-yank-prefix "> "
message-yank-cited-prefix "> "
message-send-mail-function 'message-send-mail-with-sendmail
message-yank-prefix "> "
message-yank-cited-prefix "> "
message-send-mail-function 'message-send-mail-with-sendmail
+ message-sendmail-envelope-from 'header
message-indent-citation-function '(message-indent-citation
mdw-trim-spaces-after-citing))
message-indent-citation-function '(message-indent-citation
mdw-trim-spaces-after-citing))