qmail+vpopmail+qmailadmini send mail very slowly

[Rick Yu]

hi,
  I install qmail and vpopmail with
 ./configure --enable-roaming-users=y --enable-hardquota=50000000 
--enable-default-domain=localhost.localdomain --enable-ucspi-dir=../ucspi-tcp-0.88 
--enable-passwd=n;

  and crontab -e

20 * * * * /home/vpopmail/bin/clearopensmtp 2>&1 >/dev/null

  
  I can receive email very quickly, but send email is very slow, and sometimes be 
interrupted,
how to speed up the smtp process?

  Thanks!

            Rick Yu
            [EMAIL PROTECTED]