Install addresses-goodies-for-gnustep by entering the following commands in the terminal:
sudo apt update sudo apt install addresses-goodies-for-gnustep
Personal Address Manager for GNUstep (Goodies)
This package contains a couple of things that might be of use: adgnumailconverter A tool that will merge your GNUMail address book into the Addresses database. . adserver A stand-alone Addresses network server. . adtool A command-line tool for address database manipulation.