Fix bug #8595 with setting mailclient-send-it on MS-Windows.

 lisp/mail/sendmail.el (send-mail-function): On MS-Windows, default to
 mailclient-send-it even if window-system is nil.

lisp/ChangeLog

 2011-05-07  Eli Zaretskii  <eliz@gnu.org>
 
+	* mail/sendmail.el (send-mail-function): On MS-Windows, default to
+	mailclient-send-it even if window-system is nil.  (Bug#8595)
+
 	* term/w32console.el (terminal-init-w32console): Call
 	get-screen-color and use its output to set the frame
 	background-mode.  (Bug#8597)

lisp/mail/sendmail.el

@@ -141,14 +141,18 @@ Otherwise, let mailer send back a message to report errors."
 ;; standard value.
 ;;;###autoload
 (put 'send-mail-function 'standard-value
-     '((if (and window-system (memq system-type '(darwin windows-nt)))
+     ;; MS-Windows can access the clipboard even under -nw.
+     '((if (or (and window-system (eq system-type 'darwin))
+	       (eq system-type 'windows-nt))
 	   'mailclient-send-it
 	 'sendmail-send-it)))
 
 ;; Useful to set in site-init.el
 ;;;###autoload
 (defcustom send-mail-function
-  (if (and window-system (memq system-type '(darwin windows-nt)))
+  (if (or (and window-system (eq system-type 'darwin))
+	  ;; MS-Windows can access the clipboard even under -nw.
+	  (eq system-type 'windows-nt))
       'mailclient-send-it
     'sendmail-send-it)
   "Function to call to send the current buffer as mail.