Sylpheed

Sylpheed is a free and simple e-mail client. This program runs on Linux, BSD, Mac OS X and Windows. The code is available on the author's site, and can be freely modified and distributed.

Sylpheed performs every task any good e-mail client does. It was designed as a lightweight client, so it will generate just plain text messages. You can attach files, however, but you won't be able to see them. Should you receive an HTML message, you will see the text in it, and the links it contains, but you won't see it in HTML format, just plain text. If you want to see the original message, in HTML format, you will need to double-click on the text/html link in the Attachment section. Your default browser will be opened to show you the message. This client has a built-in program to detect and stop junk mail. You can adjust the program's settings to filter the messages you don't want to see. You can also set the program to accept messages, if they have a certain predefined signature. If you want, you can set the program to use an external editor to compose messages.