Install bld by entering the following commands in the terminal:
sudo apt update sudo apt install bld
Black List Daemon, automatically build blacklists
BLD stands for "black list daemon" and is intended to build blacklists using simple rules based on a maximum number of submissions of the same IP address during a minimum time interval. BLD was primarily designed to fight against dictionary-based spams (by making the MTA report to BLD any host that tries to send a mail to an unknown user) but can be used by any application that needs a blacklist based on connection rate limits. . This package contains the server.