Why you need a threaded mailreader
There are many reasons to switch to mutt for mail. It's fast, it reads a number of popular mailbox formats natively, it's easily configurable, and it makes life a lot easier in a lot of little ways.

But if I had to pick one feature that takes the cake, it's threaded mailreading.

An example is almost certainly the easiest way to explain this.

Here's a folder with some mail in it, sorted by date:



Lots of messages, and you can easily tell what came in when. But there are a lot of different conversations going on here, and it's extremely difficult to track them unless you're following along in realtime, and even then, it can be tricky.

One simple change - display messages as a hierarchy, with responses nested underneath the original messages - makes this a >LOT< easier. On top of which, it gives you at least three capabilities that aren't present with date sorting:

1. You can see which messages are responses to responses, rather than responses to the original thread.
   
2. You can tell when the subject line of a thread changes, even though it's still a response (which brings me to another annoyance - if you're going to reply to a message but change the subject line, you should also remove the in-reply-to header).
   
3. You can refile an entire thread at once.
   

Here's the same folder, presented in threaded view: