postfix configuration: Changing password not possible

I believe I have some errors in my postfix.. When I change my email password in ispconfig, I cannot send emails anymore on my thunderbird (starttls/normal password settings).
I read somewhere that there should be passwords in /etc/postfix/sasl_passwd but it's a blank file.
Maybe I'm missing a map file or mysql connection is not working..
How can I diagnose this? Many thanks, -t
System: Centos 9, ISPConfig 3.2.

 

Check the mail log. In a default ISPConfig installation Postfix uses Dovecot SALS Auth for authentification so the configuration file can be found in the /etc/dovecot folder.

 

Many thanks -- it started working by itself