Earthlink seem to be running a brain-damaged mail server :)  The problem
is that the user [log in to unmask] has had his internet access cut off,
but the server is throwing an error back ostensibly for <all> of the
Earthlink users it found in the BSMTP job, even though three of them aren't
experiencing any problem at all.  If you delete [log in to unmask] from
your list this error should stop.

Nathan