PHP hosting questions

[rybo]

I'm writing a webmail application in PHP. It saves e-mails outside of the

http://www directory

so saved information (such as e-mails, address books, etc) don't have world-access through Apache (or any web-server for that matter). This works fine on my machine because I have access to the whole file system, but how could I get this to work for people that might use the script on a hosting service? I've never really used one before, so I don't know how stuff like this is treated.

Thanks in advance.