Look at
http://archives.postgresql.org/pgsql-hackers/2005-04/msg00167.php
This has cut off the message starting at the useful comment, which
read like this:
From a development standpoint, that suggests a couple of TODO items:
* Look harder at whether VACUUM can scan the index in physical instead
of logical order.
* See whether ordinary btree maintenance (ie page splits) can do
anything to maintain/improve the physical ordering of the index.
I suppose something is being rather lax about parsing unix mbox format
and is thinking any line starting with "From " is a new message. If
I'm right, this message will be busted as soon as it gets into the
archives, too ...
regards, tom lane