I had to deal with a whole load of bounces of attachments of type .dll
which were rejected by the recipient -- I did not record exactly who
but I this Art was one of them.
  I understand the "trick" is to change the name to, say, .lld and
then the file needs to be renamed at the other end.  This does stop the
automatic installation which is what the filters are trying to avoid.
==John ffitch