FYI, Andrew Strong wrote an excellent guide

http://www.andrews-corner.org/mutt.html

Hey man... i dont know much about mutt mail client ..i use claws mail (its a GUI interfaced software) here's the manual link

http://www.mutt.org/doc/manual/

let me know what u find

Are you having fetchmail put the mail into your system mailbox?

laoxu, pretty hard to tell what is wrong without seeing your .fetchmailrc and .muttrc.

Welcome to the forum and Slackware

btw- I use mutt and fetchmail with Slackware.

This isn't going to help your problem (and it's been a while since I configured mutt/fetchmail/procmail, though I do use them every day), but I just thought I would mention offlineimap. gmail supports IMAP and I much prefer offlineimap to fetchmail+procmail, especially when using multiple accounts. I have three IMAP accounts and one POP3 account working with mutt. Adding more IMAP accounts just requires modifying my .offlineimaprc (and .muttrc), whereas adding a POP3 account would require modifying .fetchmailrc, .procmailrc, and .muttrc, and to keep everything separate (which I like to do), it would require making a .fetchmailrc.other and .procmailrc.other, for example, and calling
and, from within .fetchmailrc.other, setting my mda as
offlineimap is just simpler to use when IMAP is available. Just my opinion of course. I'm not going to lookup all of the options in my configuration files, but I will just post them here (minus any personal details like e-mail and password).

.fetchmailrc:
where username is my Linux username, my@email.com is my e-mail address, xxxx is my password (make sure this file has 600 permissions), and /home/username/Mail/certs is where I keep my certificates (you will have to generate or locate the proper certificate for whatever server you are using, and I cannot remember how to do that at all, so you're on your own there). Note that this is being used for hotmail, but it should work for any POP3 account.

.procmailrc:
where username is, again, your Linux username, and $HOME/mail/hotmail is where I am keeping this mail (you would obviously want to change this).

My script for receiving mail (I run this as a cron job):
Of course you can remove the offlineimap line if you don't use it. I also call this script from my .muttrc when pressing 'I' to manually receive mail:
where that is the location of my script. Everything else should be strictly .muttrc configuration, which several tutorials and manuals should describe. I would still suggest offlineimap if you can get away with it -- you only have to deal with .offlineimaprc and .muttrc, and there is no need to play with fetchmail/procmail interactions.

sorry guys i wasn't at home this weekend,so i cound not read you replies until today,thanks for all of you.

here i wanna say is that i am not talking about mutt or fetchmail problem,i am talking about mail problem.to explain this ,i write a mail just now :

"mail to root@localhost -s "can you receive ?" < mesg.txt"

and here is my mail log:

Oct 18 17:20:45 lx sendmail[2355]: o9I9KjVk002355: from=root, size=253, class=0, nrcpts=7, msgid=<201010180920.o9I9KjVk002355@lx.lx.com>, relay=root@localhost
Oct 18 17:20:45 lx sendmail[2355]: o9I9KjVk002355: to=you,to,root@localhost,receive,it,can,???, ctladdr=root (0/0), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=210253, relay=[127.0.0.1] [127.0.0.1], dsn=4.0.0, stat=Deferred: Connection refused by [127.0.0.1]

so i think maybe there are some packages lack in system ?
or i should open or close something ?

it's explained in the guide I linked, you need msmtp

http://www.andrews-corner.org/mutt.html#sending

easier than setting up sendmail with a smarthost.

Try

cat msg.txt | mail root@localhost

ok,thanks man,it works after i install msmtp.....