I had a # in my mail_db_password and spent the last 2 hours trying to figure out why I couldn't connect by IMAP. A # is only allowed if the connect string is wrapped in quotes.

Remove all configuration for MySQL and configure PostgreSQL as the main
database.

All *_mysql_* options have been changed to *_db_* options.

Postgres requires the database user to have a password in order to
connect via localhost. The db_admin_password option is used to set the
password of the admin user (usually postgres).