[extropy-chat] META: List attachments

[BillK]

If the extropy-chat mail software is not blocking attachments, then it
probably should.

Most lists I am in do not allow attachments, in order to remove the
risk of mailing viruses to list members.

The standard advice is to never open mail attachments or click on them
(especially if you are not expecting to receive an attachment),
without first scanning them with your antivirus software.

BillK