PHP - Email-in posting (like Posterous)?

I have a small web app to which users upload photos. I want to let them email in their photos (from their iPhones/Android phones) and a number associated with that photo. It'd be kind of like posterous but only allow emails with one photo and one n开发者_运维知识库umber.

How could this be done?

I see two ways, but I'm not sure if I'm even close. 1) Have one email (like Posterous) that users send mail to, then send to it from the same email that their account is under. 2) Have a unique email for every user that they can email to. (But this has the problem that anyone could send emails to the unique email.)

To do either way, you'd need to have a filter on the mail server that takes incoming mail and fires off a script that inserts that information into the db, or does whatever else with it.

It's not too hard, but usually requires admin (or root) access to the machine, i.e., can't be done in a shared hosting environment.