I did this tutorial: https://www.howtoforge.com/perfect-server-debian-10-buster-apache-bind-dovecot-ispconfig-3-1/ now I can't see my limits and billing module doesn't work properly. from till: Which tutorial did you use to install the server and which MySQL or MariaDB did you install? I just ask because this error is typical when an incompatoble database version has been installed.
I have a server based on that setup here and client limits and Billing Module are working on that system as far as I can see, then guide installs MariaDB. Maybe you installed a newer MariaDB version or MySQL instead when you encounter issues. Another possibility is that you enabled some strict modes in MariaDB, which might cause similar issues to using a newer MariaDB version.
Did you follow the guide to the letter or did you install different or newer software versions? Which exact database version do you have installed?
What you can try when you use MariaDB is this, set: sql_mode=NO_ENGINE_SUBSTITUTION in /etc/mysql/mariadb.conf.d/50-server.cnf inside the [mysqld] section and restart MariaDB.
I followed it to the letter. I'm having a hard time finding sql_mode=NO_ENGINE_SUBSTITUTION in that file.
You'll probably find it in /var/log/apache2/error.log But I don't think that the RoundCube error is caused by that MySQL setting, it probably is related to something else that was changed or configured on the server.
