Install eximon4 by entering the following commands in the terminal:
sudo apt update sudo apt install eximon4
Description:
monitor application for the Exim MTA (v4) (X11 interface)
Eximon is a helper program for the Exim MTA (v4). It allows administrators to view the mail queue and logs, and perform a variety of actions on queued messages, such as freezing, bouncing and thawing messages.
Homepage: https://www.exim.org/
Version: 4.90.1-1ubuntu1
Section: universe/mail