$ sudo apt-get update
$ sudo apt-get install dovecot-dbg 

dovecot-dbg is installed in your system.

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

$ sudo dpkg-query -l | grep dovecot-dbg *

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

dovecot-dbg package basic information: