Without having your own server,
all I can think of is having a PHP script
periodically go into a pop3 email account
and look for attachments. Not very elegant,
as it will have to run via a CRON job, and
somehow have to know what to do with
Stuff like this?
Otherwise, if you had your own dedicates server (Apache, PHP5) ... I think it
could be done with some software, and it would be done automatically when
an email was received.
This looks like a big project.