[Dovecot] Dovecot-auth <defunct>

We have used qpopper on our email server RH 9 for long. But recently as the number of people using the server has increased too fast we have to switch to dovecot. Things seem to be OK with the rate users post and receive emails. But from that time very often I see this when top:

. dovecot-auth <defunct>

And some people sometimes have to restart their outlook to receive emails

Could any give us a hand to solve this problem.

Thanks and regards,