Removing plain passwords from auth.log

I'm using some docker images to deploy a mail server (https://github.com/docker-mailserver/docker-mailserver). The MTA is postfix, with TLS configuration and using LDAP for login. I can login to the SMTP server and send emails but is showing the login password in plain text in auth.log

Jul 26 10:57:01 mail saslauthd[979]:                 : num_procs  : 5
Jul 26 10:57:01 mail saslauthd[979]:                 : mech_option: kopano_gateway
Jul 26 10:57:01 mail saslauthd[979]:                 : run_path   : /var/run/saslauthd
Jul 26 10:57:01 mail saslauthd[979]:                 : auth_mech  : rimap
Jul 26 10:57:01 mail saslauthd[979]:                 : using accept lock file: /var/run/saslauthd/mux.accept
Jul 26 10:57:01 mail saslauthd[979]:                 : master pid is: 0
Jul 26 10:57:01 mail saslauthd[979]:                 : listening on socket: /var/run/saslauthd/mux
Jul 26 10:57:01 mail saslauthd[979]:                 : using process model
Jul 26 10:57:01 mail saslauthd[979]:                 : forked child: 986
Jul 26 10:57:01 mail saslauthd[979]:                 : forked child: 987
Jul 26 10:57:01 mail saslauthd[979]:                 : forked child: 988
Jul 26 10:57:01 mail saslauthd[979]:                 : forked child: 989
Jul 26 10:57:01 mail saslauthd[979]:                 : acquired accept lock
Jul 26 10:57:36 mail saslauthd[979]:                 : released accept lock
Jul 26 10:57:36 mail saslauthd[979]: auth_rimap: sending saslauthd LOGIN "user1" "password"
Jul 26 10:57:36 mail saslauthd[979]: auth_rimap: sending saslauthd LOGOUT
Jul 26 10:57:36 mail saslauthd[979]: auth_rimap: [user1] saslauthd OK [CAPABILITY IMAP4rev1 LITERAL+ CHILDREN XAOL-OPTION NAMESPACE QUOTA IDLE] LOGIN completed
Jul 26 10:57:36 mail saslauthd[979]:                 : auth success: [user=user1] [service=imap] [realm=] [mech=rimap]

I could edit rsyslog.conf and change the line

auth,authpriv.*         /var/log/auth.log

by

auth,authpriv.*         /dev/null 

but I would like to have auth.log not showing the passwords. I suppose I could change config in /etc/supervisor/conf.d/saslauth.conf because it seems like saslauthd commands are being exec with flag -d (debug) by default:

[program:saslauthd_rimap]
startsecs=0
autostart=false
autorestart=true
stdout_logfile=/var/log/supervisor/%(program_name)s.log
stderr_logfile=/var/log/supervisor/%(program_name)s.log
command=/usr/sbin/saslauthd -d -a rimap -r -O %(ENV_SASLAUTHD_MECH_OPTIONS)s
pidfile=/var/run/saslauthd/saslauthd.pid

but if I try to mount that file in the docker-compose.yml, with the -d flag removed, saslauthd can't start properly:

/home/admin/postfix/saslauth.conf:/etc/supervisor/conf.d/saslauth.conf

Jul 26 11:58:44 mail saslauthd[3373]:                 : Cannot start saslauthd
Jul 26 11:58:44 mail saslauthd[3373]:                 : Another instance of saslauthd is currently running
Jul 26 11:58:45 mail saslauthd[3378]:                 : could not lock pid file /var/run/saslauthd/saslauthd.pid: Resource temporarily unavailable

Is it any way to disable debug mode for saslauthd in a docker container using environment variables or something? Or what would be the right way to hide passwords in auth.log?