$ sudo apt-get update
$ sudo apt-get install libsendmail-milter-perl 

libsendmail-milter-perl is installed in your system.

Make ensure the libsendmail-milter-perl package were installed using the commands given below,

$ sudo dpkg-query -l | grep libsendmail-milter-perl *

You will get with libsendmail-milter-perl package name, version, architecture and description in a table

libsendmail-milter-perl package basic information: