I have just rebooted the server after a software update, but the Dovecot services did not restart.
✖ Dovecot LMTP LDA is not running (port 10026).
✖ IMAPS (dovecot) is not running (port 993).
✖ Mail Filters (Sieve/dovecot) is not running (port 4190).
After running the mailinabox command - the services start OK.
When I review the /var/log/mail.log I noticed the error:
Mar 21 13:30:32 mail spampd[2179]: WARNING!! Error in process_request eval block: /usr/sbin/spampd: socket connect failure: Connection refused
It sounds like a race condition when spampd has given up waiting for the Dovecot service to start.