Index: lisp/nnmail.el
===================================================================
RCS file: /usr/local/cvsroot/gnus/lisp/nnmail.el,v
retrieving revision 7.9
diff -u -r7.9 nnmail.el
--- lisp/nnmail.el	20 May 2004 08:02:40 -0000	7.9
+++ lisp/nnmail.el	8 Jul 2004 23:10:35 -0000
@@ -574,6 +574,15 @@
   :group 'nnmail
   :type 'boolean)
 
+(defcustom nnmail-split-fancy-lowercase-expanded nil
+
+  "Whether to lowercase expanded entries (i.e \\N) or leave them as-is
+when using fancy splitting. This avoids the creation of multiple
+groups when users send to an address using different case (i.e 
+mailing-list@domain vs Mailing-List@Domain)."
+  :group 'nnmail
+  :type 'boolean)
+
 ;;; Internal variables.
 
 (defvar nnmail-article-buffer " *nnmail incoming*"
@@ -1464,8 +1473,11 @@
 	      (setq N 0)
 	    (setq N (- c ?0)))
 	  (when (match-beginning N)
-	    (push (buffer-substring (match-beginning N) (match-end N))
-		  expanded))))
+	    (let ((tmp-match (buffer-substring (match-beginning N)
+					       (match-end N))))
+	      (if nnmail-split-fancy-lowercase-expanded
+		  (push (downcase tmp-match) expanded)
+		(push tmp-match expanded))))))
       (setq pos (1+ pos)))
     (if did-expand
 	(apply 'concat (nreverse expanded))