attachment curfew

Oh, these email virii, what joy they bring to my life.

There are a lot of email virii flying around the list, due to the fact
that they all forge From headers and some of them end up being to
list@rhizome.org and from a list subscriber. Ideally I would like to
implement something that filters these on the server, but the server's
pretty high-load these days and we're actually scrambling to move
everything to newer faster machines in a week or two.

In the meantime, I have shut off the ability to send attachments
through the Raw list. This might also affect your ability to send HTML
email, though for most of you it shouldn't. This is a temporary patch.
Hopefully within a month you'll be able to send attachments again, but
not virii.

Francis