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

dovecot-gssapi is installed in your system.

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

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

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

dovecot-gssapi package basic information: