maildir structure

[LRiva]

Hello.
I have two rather stupid questions as I'm a newbie with Qmail.
I've just installed Qmail and set it to use maildir-like mailboxes.
The question is:
Mutt ask me to specify a file to use as spool mailbox: how should I set this ?
What are the function of the /tmp and /cur maildir subdirectories ?

Excuse me if they're RTFM, but I didn't found the answers in the manuals...

bye,
Lorenzo