[Dovecot] Post-login script with LDAP virtual users

[Hideo GOTO]

Dear sirs,

I'm working on Post-login script for migrating 40K Courier-imap users to
Dovecot.

After reading related topics about post-login script in your
documentation, mailing list, I cannot remove the problem described
here-below.
Is there any special config to add when users are virtual
(authentication and user info is fed by LDAP server).

I would be grad if anyone could give me advise.

Phenomena:
==========
Although the authentication and script execution is successfully done,
Pop3 session is aborted just after that, leaving the following error
message to syslog:

/var/log/maillog:
Feb 7 17:45:58 pop3migr dovecot: pop3(vuser1): Post-login script denied
access to user vuser1

cf.
"vuser1" is UID of a virtual account on the LDAP tree. Maildir is
located at /var/spool/postfixdata/%u/Maildir, and is owned by linux
local user "mailuser".

Dovecot works perfect ,if post-login script configuration is commented out.

Environment:

Dovecot: dovecot-2.0.9 (built from source tar ball)
OS: Linux / 2.6.30.10-105.2.23.fc11.x86_64 (Virtual machine on a xen server)
Maidir: tested both with local file system and NFS (ext3, xfs)
client: Using telnet on pop3 TCP port.

All the pop3 users are virtual and does not have local login account
('authentication and user information is given by LDAP server).
SMTP service is managed by Postfix: ( A single local login account is
writing all mails to Maildir for all the virtual users. )

Thanks in advance.