Install courier-authlib-userdb by entering the following commands in the terminal:
sudo apt update sudo apt install courier-authlib-userdb
Description:
userdb support for the Courier authentication library
This package contains the userdb support for the Courier authentication library. Userdb is a simple way to manage virtual mail accounts using a GDBM-based database file.
Homepage: https://www.courier-mta.org/
Version: 0.68.0-4build1
Section: universe/mail