akonadi-backend-mysql - 4:18.08.3-7~deb10u1 main

Akonadi is an extensible cross-desktop Personal Information Management (PIM)
storage service. It provides a common framework for applications to store and
access mail, calendars, addressbooks, and other PIM data.
.
This package installs everything what's needed for Akonadi to work with MySQL
as underlying data storage engine. By default, a local MySQL server instance
will be started for each user. Alternatively, connection to an external MySQL
database is supported as well.