If your seeing messages from mailing lists that are seriously old,
there is a reason. One of our mailing lists had not been correctly
adding mail to it's mbox due to a file permission error, and as such was
pushing the messages into a 'shunt' queue. Unfortunately I wasn't
specific enough when 'unshunting' the messages and caught a bunch of
other mailing lists at the same time. I apologize for any inconvenience
this may cause you.