First things first: how mail works

There are "mail servers" (correctly named: mail transfer agents), which act like a postman: either they know the user to whom to deliver the mail themselves (then they do that) or they send the mail to some other MTA, which does the same (either deliver the mail or send it onwards), until the mail is finally delivered. The same happens in the other direction: you send a mail, the MTA responsible for you picks it up and the delivery process like described above starts. Examples for mail servers are "sendmail", but also "exim" and M$$ "Exchange Server".

Then there are "mail user agents", or mail clients, for short. One of them is Mutt (another example, although a pretty poor one, wold be "Outlook"). These provide some frontend for the user (graphical or otherwise) and handle the communication with the MTAs, mainly the one MTA responsible for the serving of the mail address you use. (a "mail address" is basically a sort-of account on a MTA).

Communication in the mail world

MTAs use a certain protocol to communicate, called SMTP (simple mail transfer protocol). But it is obvious that the clients (MUAs) and the servers (MTAs) need some way to communicate too. There are several ways to do this and the most common ones are IMAP (Internet Message Access Protocol) and POP3 (Post Office Protocol 3). Both allow the client (your mail program) to manipulate mails either stored at the server or delivered to you locally.

What you have to do:
Now, after much explanation, here is what you need to do: you need to figure out what form of mail delivery yahoo-mail offers. Further you need to figure out the server name of their mail service (probably "mail.yahoo.com" or something such). It might be that they only offer their service via a web interface. In such a case you can't use your mail client but have to use what they offer. But maybe they offer some "POP3" or "IMAP" access. In such a case you need to get the connection data necessary (your mail client will perhaps tell you in the configuration dialogue what it needs to know, usually a server name and a port number), then you need to configure the email account you want to use (your email address) and maybe some password.

As do neither use mutt nor Yahoo mail i cannot tell you exactly what to do, so will have to either wait for someone more knowledgable than me or make do with my general advice. If you try and get stuck you can always ask more detailed questions for (hopefully) more detailed answers.

I hope this helps.

bakunin