--- a/mail.rst	Mon May 17 23:56:31 2010 +0300
+++ b/mail.rst	Sat May 29 20:05:40 2010 +0300
@@ -56,4 +56,21 @@
 
 ** Stallman warn about Google.
 
-  http://www.mail-archive.com/gnu-emacs-sources@gnu.org/msg00302.html
\ No newline at end of file
+  http://www.mail-archive.com/gnu-emacs-sources@gnu.org/msg00302.html
+
+* Storage format for email.
+
+** mbox.
+
+  http://tools.ietf.org/html/rfc4155
+                The application/mbox Media Type (Category: Informational)
+  http://en.wikipedia.org/wiki/Mbox
+
+** maildir.
+
+  http://en.wikipedia.org/wiki/Maildir
+
+** MH mailbox format.
+
+  http://en.wikipedia.org/wiki/MH_Message_Handling_System
+