Install courier-maildrop by entering the following commands in the terminal:
sudo apt update sudo apt install courier-maildrop
Description:
Courier mail server - mail delivery agent [transitional package]
This dummy package depends on standalone maildrop package and can be safely removed.
Homepage: http://www.courier-mta.org/
Version: 2.9.1+0.78.0-2ubuntu2
Section: universe/mail