Hello!
I am testing your product and I need a little help in setting up the iredmail server.
I want to save user emails to a custom directory, please tell me how I can do this?
Do I need to create a trigger in the MariaDB database or is it possible to set this up using built-in tools?

The storage of emails is chosen during setup.  Normally it defaults to /var/vmail and you will find the emails stored there in text form.  In folders named the name of the email addresses.  You can copy those folders to wherever you like and the emails are in text form.  But I believe you can't change the location once you installed in any easy way.  It is better to reinstall with the directory chosen during install.