[Qmail] ERR unable to scan $HOME/Maildir

Very strange.

Just picking up a new customer, the company mail server was made by the last IT consulting company. The server is SME Server (previously called e-smith server). Today, one user cannot access his pop3 account using Microsoft Outlook while other users does not have any problem. The most strange happening is that he can access his web mail without problem.

I try to telnet the mail server IP with port 110:

telnet the.mail.server.ip 110
USER username
PASS userpassword

The error comes out as follows:

ERR unable to scan $HOME/Maildir

After searching, all the reasons are the permission problem. I have checked all the permission, they are correct. I even reset the user right on the Maildir. There was no luck at all !!

I checked that the user has a lot of email (over 1.5GB). Luckily, I have some experience on qmail server. I begin to doubt that qmail needs some more memory to handle email. So, I changed the softlimit of the pop3d. The path is

pop3:
/var/qmail/supervise/pop3d/run
or
pop3s:
/var/qmail/supervise/pop3ds/run

After restarting the qmail, the problem fixed !!!!