$ sudo apt-get update
$ sudo apt-get install gkrellm-mailwatch 

gkrellm-mailwatch is installed in your system.

Make ensure the gkrellm-mailwatch package were installed using the commands given below,

$ sudo dpkg-query -l | grep gkrellm-mailwatch *

You will get with gkrellm-mailwatch package name, version, architecture and description in a table

gkrellm-mailwatch package basic information: