Forgot to mention, sorry. My Cyrus 3.4.4 is running on the latest FreeBSD 13.1-RELEASE-p3 amd64. I am not a programmer, so I installed cyrus-imap34 package instead of the port, thus with no configuration, to its default destination:
/usr/local/bin/,
/usr/local/cyrus/sbin/,
/usr/local/cyrus/libexec/,
/usr/local/lib/libcyrus*,
/usr/local/lib/perl5/,
/usr/local/libdata/,
/usr/local/include/cyrus/,
/usr/local/share/,
/usr/local/cyrus/man/man8/,
/usr/local/man/,
/usr/local/etc/
I found now
cyr_expire in cyrus/sbin, with ipurge, mbexamine, mbtool, reconstruct, tls_prune, unexpunge, and many other tools besides as well. I will learn and try to execute them — thank you very much, dear Nic!