How can I creat a mialbox for Mutt?

[YangPeng Ou]

I install the Mutt on my computer with Ubuntu Breezy yesteday.
When I open it first ( $mutt), the program ask me for whether I creat directory
Mail, I agree. However, the program report that there is no /var/mail/p
exiting(error2)
So I creat a directory /var/mail/p, and open Mutt again, but it report /var/mail/p
is not a mailbox...
How can I deal with it?