Exim (v4) is a mail transport agent. this package contains header files that can be used to compile code that is then dynamically linked to exim's local_scan interface.

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