(sendmail-coding-system): New variable.

(sendmail-send-it): Perform code conversion on sending mail
according to sendmail-coding-system.

lisp/mail/sendmail.el

@@ -551,6 +551,9 @@ the user from the mailer."
 ;; This does the real work of sending a message via sendmail.
 ;; It is called via the variable send-mail-function.
 
+(defvar sendmail-coding-system 'coding-system-iso-2022-7
+  "Coding system to which to encode the mail.")
+
 (defun sendmail-send-it ()
   (require 'mail-utils)
   (let ((errbuf (if mail-interactive
@@ -691,7 +694,8 @@ the user from the mailer."
 		(re-search-forward "^To:\\|^cc:\\|^bcc:\\|^resent-to:\
 \\|^resent-cc:\\|^resent-bcc:"
 				   delimline t))
-	      (let ((default-directory "/"))
+	      (let ((default-directory "/")
+		    (coding-system-for-write sendmail-coding-system))
 		(apply 'call-process-region
 		       (append (list (point-min) (point-max)
 				     (if (boundp 'sendmail-program)