I used to use claws but switched over to Modest a while back I like both programs, Modest is simpler and integrates with your contacts (its broken with Gmail right now so wait till the april 20th update to install) and also can run in the background with the LED lighting up when email comes in. Claws is as Tim says a 'traditional' email client and it is a standalone product. If you like the features and power of a desktop client and don't mind using a stylus for operation then Claws is definitely the way to go.