dovecot - Apr 2009 - An issue of I login my mail server from webmail client

Dear all:

I have a really strange issue, that is when I login my mail server from
webmail client (I used SquirrelMail, by the way, I have modified
squirrelmail's timeout value, that means not since squirrelmail timeout), I
will got timeout issue when I login about 5PM ~ 10PM everyday (it works fine
on other time, I also check my cron, that looks no problem), and during this
time, I also cannot connect my 993 port with openssl like this:

openssl s_client -connect myDomainName:993

But when I use mail client (such as outlook) to access dovecot, that works
fine, and during 5PM ~ 10PM, my web site also works fine, and once I restart
computer if I can not login during 5PM ~ 10PM from webmail client. that will
work fine.

can you try to help me? below is my configure of dovecot.

*dovecot -n
# 1.0.7: /etc/dovecot.conf
log_path: /var/run/dovecot/maillog
info_log_path: /var/run/dovecot/maillog
protocols: imaps
ssl_parameters_regenerate: 0
verbose_ssl: yes
login_dir: /var/run/dovecot/login
login_executable: /usr/libexec/dovecot/imap-login
mail_location: maildir:~/Maildir
mail_debug: yes
auth default:
  mechanisms: plain login
  passdb:
    driver: pam
  userdb:
    driver: passwd
  socket:
    type: listen
    client:
      path: /var/spool/postfix/private/auth
      mode: 432
      user: postfix
      group: postfix
plugin:
  convert_mail: mbox:~/Mail:INBOX=/var/mail/%u*

-- 
Best Regards

Alan Zheng