Install courier-authlib-pipe by entering the following commands in the terminal:
sudo apt update sudo apt install courier-authlib-pipe
Description:
External authentication support for the Courier authentication library
This package contains external authentication support via pipes for the Courier authentication library. The authpipe module is a generic plugin that enables authentication requests to be serviced by an external program, then communicates through messages on stdin and stdout.
Homepage: https://www.courier-mta.org/
Version: 0.68.0-4build1
Section: universe/mail