[Dovecot] redirecting temp email files to another directory

[JANE CUA]

Here's the dovecot -n output:
# 1.1.7: /usr/local/etc/dovecot.conf
# OS: Linux 2.6.18-92.1.22.el5PAE i686 CentOS release 5.2 (Final)
log_path: /var/log/dovecot.log
info_log_path: /var/log/dovecot-info.log
ssl_disable: yes
disable_plaintext_auth: no
login_dir: /usr/local/var/run/dovecot/login
login_executable: /usr/local/libexec/dovecot/imap-login
login_greeting_capability: yes
mail_privileged_group: mail
mail_location: mbox:~/:INBOX=/var/spool/mail/%u
auth default:
  passdb:
    driver: pam
  passdb:
    driver: passwd
  passdb:
    driver: shadow
  userdb:
    driver: passwd

sample temp files that gets create in /var/spool/mail
-rw------ jane mail _43398509485894865jane
-rw------ jane mail jane.lock

other users create these files randomly as well in /var/spool/mail, /var/spool/mail is an NFS mount. 

Thank you,
Jane