Install couriergraph by entering the following commands in the terminal:
sudo apt update sudo apt install couriergraph
Description:
Mail statistics RRDtool frontend for Courier-{POP,IMAP}
Couriergraph is a very simple mail statistics RRDtool frontend for Courier-POP & Courier-IMAP that produces daily, weekly, monthly and yearly graphs of mail server's activity (logins, traffic, etc).
Version: 0.25-4.4
Section: universe/admin