mutt is for those willing to put out some effort and learn something
Mutt is not designed to suit everyone, including those without basic knowledge about the MailConcept, or those unwilling to perform configuration. Mutt is also not designed for the mass of "average users", although it works well for them too. For those who prefer a client to "just work somehow" rather than give dedicated best performance as Mutt does, they are probably better suited to use other mail programs.
If you spend a little more time to set it all up properly, it will quickly pay off in your daily work. What you save with "ready-to-use" all-in-one tools at the beginning, you lose later compared to the power of Mutt and its tools. While mutt's defaults might satisfy basic use, to adapt it well to your personal needs you must put in a little extra effort. This includes compilation setup and run-time configuration. Also employing the proper suite of tools to add functionality a MUA is not intended to provide.
If you need MTA functionality, use an MTA. Generic MIME handling? Try mailcap. If you need encryption use an encryption program. A mixed-use client typically won't offer as good, capable, easy to use, secure, and efficient an implementation of the desired functions as a dedicated tool.
Here you can find some reviews of other sites to help you decide whether Mutt is worth the effort to get started with it. If you find some new ones, append them.
- A Man And His Mutt: http://www.melonfire.com/community/columns/trog/article.php?id=98
- Mark Stosberg's Mutt Fan & Tip Page: http://mark.stosberg.com/Tech/mutt.html
- Jack Mottram on Mutt: http://lifehacker.com/5574557/how-to-use-the-fast-and-powerful-mutt-email-client-with-gmail
- Sukrit Dhandhania http://www.linuxuser.co.uk/tutorials/get-started-with-mutt