Kolab 2.4 kolab_smtp_access_policy exit status 1

[GrK]

Hi there,

I made a fresh install of kolab 2.4 on a CentOS 6.3 following this 
guide 
http://docs.kolab.org/en-US/Kolab_Groupware/2.4/html/Community_Installation_Guide/index.html
Installed :
kolab-2.4-4.el6.kolab_2.4.noarch
pykolab-0.4.14-3.el6.kolab_2.4.noarch


I can send mail via roundcude but when I try sending throung 
Thunderbird, I got an error "3.4.5 Server configuration problem"

And here is what I can find in maillog :

Dec 18 00:47:03 mail postfix/submission/smtpd[16713]: connect from 
unknown[10.59.81.102]
Dec 18 00:47:04 mail postfix/submission/smtpd[16713]: DFE36800EC: 
client=unknown[10.59.81.102], sasl_method=PLAIN, sasl_username=grk
Dec 18 00:47:05 mail postfix/spawn[16718]: warning: command 
/usr/libexec/postfix/kolab_smtp_access_policy exit status 1
Dec 18 00:47:05 mail postfix/submission/smtpd[16713]: warning: 
premature end-of-input on private/submission_policy while reading input 
attribute name
Dec 18 00:47:06 mail postfix/spawn[16718]: warning: command 
/usr/libexec/postfix/kolab_smtp_access_policy exit status 1
Dec 18 00:47:06 mail postfix/submission/smtpd[16713]: warning: 
premature end-of-input on private/submission_policy while reading input 
attribute name
Dec 18 00:47:06 mail postfix/submission/smtpd[16713]: warning: problem 
talking to server private/submission_policy: Success
Dec 18 00:47:06 mail postfix/submission/smtpd[16713]: DFE36800EC: 
reject: DATA from unknown[10.59.81.102]: 451 4.3.5 Server configuration 
problem; from=<xxx at xxx.xxx> to=<yyy at yyy.yyy> proto=ESMTP 
helo=<[10.59.81.102]>

Can someone help me or give me a key on how to handle this issue ?

Thank's,