--- message.el.orig	Sat Nov  6 04:15:15 1999
+++ message.el	Thu Nov 11 19:39:26 1999
@@ -2939,6 +2939,12 @@
   (let ((system-name (system-name))
 	(user-mail (message-user-mail-address)))
     (cond
+     ;; First check if `message-id-host' is set and valid.
+     ((and (boundp 'message-id-host)
+	   (stringp message-id-host)
+	   (string-match "\\." message-id-host))
+      message-id-host)
+     ;; Then try `system-name'.
      ((string-match "[^.]\\.[^.]" system-name)
       ;; `system-name' returned the right result.
       system-name)