Allow multiple users to post via email to only one category

Howdy there all you know-more-about-wordpress-than-me folks!

I have a WP site that is for promoting a small downtown business district. We’ve got a couple of restaurants and they email out their specials every day. I’d like to set them up so that they can CC: an email address and the specials autopost to my blog.

Requirements:
–Page that will display only posts from the “restaurant specials” category (currently implemented with a custom template and modified loop)

–Ability to restrict post authors to a particular category (currently implemented with role scoper [bonus question: how do i set role scoper so that a user is not only allowed to post in only one category but also make that category the default for that user?])

–Ability for users to post via email. Currently NOT implemented because I have some concerns. Can post-via-email be configured either nativly or through a plugin to only post if the email comes from specific email addresses?

So, again, the idea is that the resturant managers can just add the post-via-email-to-the-restaurant-category-email address to their mailing list and have it automatically posted to the blog. I’m not committed to any of the above solutions (role scoper and modified template for displaying only posts of a particular category) so I’m all ears if you’ve got ideas.

Thanks!