akonadi-backend-postgresql 4:15.12.1-0ubuntu3 (amd64 binary) in ubuntu xenial

 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
 PostgreSQL as underlying data storage engine. By default, a local PostgreSQL
 server instance will be started for each user. Alternatively, connection to an
 external PostgreSQL database is supported as well.