My cyrus imap server stopped working without any real reason. It is very strange. But the recovery was to purge jansson library, reinstall it, and force-reinstall cyrus.
IMAPD stopped working. I have never seen this before. My guss is file data corruption but then, this is also very unlikely as the system is on RAID1 ZFS. (I am aware ZFS has some cache/corruption issue but my system is NOT busy at all.)
sudo pkg delete -f jansson
sudo pkg install jansson
sudo pkg install -f cyrus-imapd310
After this, IMAPD came back to life.
Yet, exim refused to deliver since the LMTP endpoint was down long time. I had to clear off the error status of the LMTP endpoint.
sudo exim_tidydb -t 1m /var/spool/exim retry
My email was bouncing for multiple days. This now reminds me that I need a way to know imapd/lmtp down. I lost a few days of emails.