Mailing list is now closed to non-subscribers.

While there, add a reference to the bugzilla.  ok djm@

README

@@ -29,10 +29,10 @@ all logins, not just when using password authentication.
 There is now several mailing lists for this port of OpenSSH. Please
 refer to https://www.openssh.com/list.html for details on how to join.
 
-Please send bug reports and patches to the mailing list
-[email protected]. The list is open to posting by unsubscribed
-users.  Code contribution are welcomed, but please follow the OpenBSD
-style guidelines[1].
+Please send bug reports and patches to https://bugzilla.mindrot.org or
+the mailing list [email protected].  To mitigate spam, the
+list only allows posting from subscribed addresses.  Code contribution
+are welcomed, but please follow the OpenBSD style guidelines[1].
 
 Please refer to the INSTALL document for information on dependencies and
 how to install OpenSSH on your system.