UX input required for small project

I need someone to layout a simple interface for a small app which will allow the user to select a number of recipients, enter a message, check 2 boxes and drop a file. The interface needs to be extremely easy to use and user-friendly.

No graphics required, just the interface layout for ease of use.

It's for an OSX app and can be supplied in any format, Xcode, PSD, hand-drawn sketch.