The service layer
The service layer abstracts access with E-mail services and is by default implemented using a modified Camel.
The Camel being used by tinymail is, however, embedded in the build procedure and has been adapted to consume less memory and less bandwidth.
For an overview of what protocols tinymail supports, check out this page.
The user interface layer
The user interface layer abstracts and implements user interface related functionality. The default implementations of tinymail implement user interface components using the Gtk+ toolkit. There's specifically support for devices like the One Laptop Per Child laptop, devices that are based on the Maemo platform like the Nokia 770 and there's support for devices on which GPE is available.