Conal is correct. The relevant section of the LISTSERV configuration
file for TEI-L is:

 # This is intended to allow text/plain, text/xml, or whatever,
 # but reject any binary attachment.
 Attachments= text

It is generally considered a security risk to permit binary format
files be attached to list e-mail. That said, I suspect that it would
be reasonable to permit things like application/tei+xml,
application/mods+xml, application/mads+xml, application/mets+xml,
application/marcxml+xml, and application/sru+xml, image/svg+xml, etc.

If any security experts want to take this up off-list, feel free.

> I believe that Stuart is actually mistaken: the TEI-L list does
> accept posts with attachments, though only if they are text files.

 Syd Bauman, TEI-L list owner
 [log in to unmask] (me personally)
 [log in to unmask] (list owner, happens to be me)