If there were awards for simplicity, then Mailsmith would score top marks. You really can't get much more simple than this text-only email client.
However, just because it's simple doesn't mean is lacks powerful features such as filtering, excellent text editing and flexible account settings. It doesn't however support IMAP accounts which means it won't be suitable for many users. There is however a thriving Google Groups forum dedicated to Mailsmith so if you can't work out how to do it, someone on the forum probably will.
When you open Mailsmith for the first time, it searches for compatible mail clients on your system. If you select the default Mailsmith setup, it automatically launches SpamSieve which does require considerable configuration. Instructions can be found in the Help menu but as you are warned beforehand, it does require accurate setup to filter your mail properly. It depends on proper setup and training in order to filter your mail accurately. In fact, setting-up Mailsmith can be rather arduous for beginners so don't expect to get up and running with it straight away.
The stand out feature of Mailsmith is its search power however. Huge swathes of messages can be searched instantly within seconds by keyword and you'll probably find it considerably quicker than your default mail client in this respect.
Mailsmith has some powerful mail filtering features but requires perseverance and patience to set it up that most users simply won't have.
