systemd=https://www.freedesktop.org/wiki/Software/systemd/[systemd]
clamav=https://www.clamav.net[ClamAV(R)]
debian=https://www.debian.org[Debian]
+debian_nonfree_archive_area=https://www.debian.org/doc/debian-policy/ch-archive#the-non-free-archive-area[Debian's non-free archive area]
tts=http://www.template-toolkit.org[Template Toolkit]
dkim_rfc=https://tools.ietf.org/html/rfc6376[RFC 6376]
ifndef::docinfo1[]
----
+Other Repository Sources
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+Certain software cannot be made available in the `main` and `contrib`
+areas of the {debian} archives, since it does not adhere to the Debian
+Free Software Guidelines (DFSG). These are distributed in the
+{debian_nonfree_archive_area}. For {pmg} two packages from the `non-free` area
+are needed in order to support the RAR archive format:
+
+* `p7zip-rar` for matching xref:pmg_mailfilter_what[Archive Objects] in the
+ xref:chapter_mailfilter[Rule system]
+
+* `libclamunrar` for detecting viruses in RAR archives.
+
+.sources.list.entry for `non-free`
+----
+deb http://deb.debian.org/debian/ buster non-free
+deb http://security.debian.org/debian-security buster/updates non-free
+deb http://deb.debian.org/debian/ buster-updates non-free
+----
+
+