Yes, it is possible, and not too difficult.  However, the archives are
supposed to be an accurate record of everything distributed by the list;
you change what this person said here, that person said there, gee, I wish
I hadn't said that, would you delete it, please? etc.  Hey, it ain't the
"Congressional Record" (in case you don't know about that, well, memebers
of congress can have inserted things they never said and remove things
they said which maybe they shouldn't have, just takes a motion which is
always honored).  Subscribers have often asked me to remove embarrassing
postings from the list archives and I always refuse;  the archives contain
postings of mine which I regret having ever posted but I will not remove
those either.  The archives are the archives.  Once you start playing with
them they are no longer archives and are not to be trusted as such.

That said, to edit the archives of your list, GET the pertinent log,
edit it and PUT it back.  Note that if it is an active log, one still
being built, you need to put the list on HOLD while you are messing
with it; if it is a finished log you need not.  This of course, is
via email as I do not trust the web interface at all.

Douglas