$ sudo apt-get update
$ sudo apt-get install dovecot-metadata-plugin 

dovecot-metadata-plugin is installed in your system.

Make ensure the dovecot-metadata-plugin package were installed using the commands given below,

$ sudo dpkg-query -l | grep dovecot-metadata-plugin *

You will get with dovecot-metadata-plugin package name, version, architecture and description in a table

dovecot-metadata-plugin package basic information: