Excessive sasl logging

Hi,
I'm using I-mscp 1.1.16 installed on debian wheezy.

I notice that sasl is logging too much:

Dec 3 02:56:06 aisha postfix/smtpd[4064]: sql plugin doing query SELECT mail_pass FROM mail_users WHERE mail_addr = '' AND status = 'ok';
Dec 3 02:56:06 aisha postfix/smtpd[4064]: sql plugin doing query SELECT mail_pass FROM mail_users WHERE mail_addr = '' AND status = 'ok';

my log has plenty of this line.

I tried to edit these files:
/etc/imscp/postfix/working/smtpd.conf
/etc/imscp/postfix/sasl/smtpd.conf
/etc/postfix/sasl/smtpd.conf
setting
log_level = 0

and restart postfix but still no luck, can you help me?

thanks

If anyone experiment this issue, I found a note in sasl readme.debian,
the debug message will always be sent out by sasl, we have to add this line to /etc/rsyslog.conf:

auth.debug /var/log/auth.debug

or (if you want to discard it):

auth.debug /dev/null