exim4-config 4.92.1-1ubuntu3 (amd64 binary) in ubuntu focal

 Exim (v4) is a mail transport agent. exim4-config provides the configuration
 for the exim4 daemon packages. The configuration framework has been split
 off the main package to allow sites to replace the configuration scheme
 with their own without having to change the actual exim4 packages.
 .
 Sites with special configuration needs (having a lot of identically
 configured machines for example) can use this to distribute their own
 custom configuration via the packaging system, using the magic
 available with dpkg's conffile handling, without having to do local
 changes on all of these machines.
 .
 The Debian exim4 packages have their own web page,
 http://wiki.debian.org/PkgExim4. There is also a Debian-specific
 FAQ list. Information about the way the Debian packages are
 configured can be found in
 /usr/share/doc/exim4-base/README.Debian.gz, which additionally contains
 information about the way the Debian binary packages are built. The
 very extensive upstream documentation is shipped in
 /usr/share/doc/exim4-base/spec.txt.gz. To repeat the debconf-driven
 configuration process in a standard setup, invoke dpkg-reconfigure
 exim4-config. There is a Debian-centered mailing list,
 pkg-exim4-users@lists.alioth.debian.org. Please ask Debian-specific
 questions there, and only write to the upstream exim-users mailing
 list if you are sure that your question is not Debian-specific. You
 can find the subscription web page on
 http://lists.alioth.debian.org/mailman/listinfo/pkg-exim4-users