How to configure log level of Postfix SQL plugin?

Symptoms

How to configure log level of Postfix SQL plugin?

Resolution

The log level is driven by two paramters in /etc/postfix/sasl/smtpd.conf file: 'sql_verbose' and 'log_level'. To completely disable verbose logging, set 'sql_verbose' value to 'no'. To manage log level verbosity, set 'sql_verbose' value to 'yes', and increase 'log_level' value from '1' to '7'.

Example:

root@server:/usr/lib/sasl2# cat /etc/postfix/sasl/smtpd.conf
pwcheck_method: auxprop saslauthd
auxprop_plugin: sql_sqlite3
saslauthd_path: /private/plesk_saslauthd
mech_list: DIGEST-MD5 CRAM-MD5 PLAIN LOGIN
auto_transition: yes
sql_engine: sqlite3
sql_hostnames: localhost
sql_database: /plesk/passwd.db
sql_select: SELECT `%p` FROM domains d, users u WHERE u.name='%u' and d.name='%r' and d.status=0 and u.status=0 and u.dom_id=d.id
sql_verbose: no
log_level: 4