These are not particularly sophisticated, but they have the merit of being small and simple. They are all command line based. It collects and stores incoming mail for onward transmission. Some basic security features are included, to stop the system being used as a spam conduit.
Configuration is extremely simple.
This is a simple SMTP client, which transmits the mail stored by the SMTP server. It works only with the server mentioned above. No special configuration is necessary. It distributes incoming mail that has been stored previously in an incoming directory. Configuration is extremely simple.