[Dovecot] Email jam problem

Dear All:

I have facing big problem at user email jam (outlook and thunderbird) how can I check the problem?(like the mail client got email very slow).

email

dovecot --version

1.0.7

dovecot -n

# 1.0.7: /etc/dovecot.conf

info_log_path: /var/log/dovecot.log

protocols: pop3

listen: [0.0.0.0]

login_dir: /var/run/dovecot/login

login_executable: /usr/libexec/dovecot/pop3-login

login_process_per_connection: no

login_process_size: 512

login_processes_count: 10

login_max_processes_count: 512

login_max_connections: 100

maildir_copy_with_hardlinks: yes

mbox_very_dirty_syncs: yes

mail_executable: /usr/libexec/dovecot/pop3

mail_plugin_dir: /usr/lib/dovecot/pop3

pop3_client_workarounds: outlook-no-nuls oe-ns-eoh

auth default:

passdb:

driver: pam

userdb:

driver: passwd