mailboxes LOCK - HELP ME

[Gilberto Dallan]

Hi all,
First of all: I search the answer on the net but I have not found it. I 
hope someone can help me.

The problem: I have installed Qpopper, Postfix, Dracd in a Redhat 7 box.
I have tested the sistem with 3 accounts. All seemed to work well.
I have added up to 30 accounts. The box had been plugged yesterday.

Today, after 3 hours of uptime, something wrong (?) is happened: mailboxes 
seemed to be locked (maillog tells me).

How can I repair the problem?

Thank you in advance