dovecot - Feb 2018 - "Stale mailbox lock file detected, will override in 0 seconds"

Hi all dovecot members,

I've received this notice from a dovecot server: "Stale mailbox lock
file detected, will override in 0 seconds"

I would like to know what it means.

I've implemented a "Mail Proxy Server" in java, which connects to
many accounts and folders, listening for incoming messages or deleted one, it
uses the IMAP protocol.
I received that message only 5 times in 60 days of logs, last time, in the same
time lapse my server has not received three messages, saying differently, the
listener (I'm using Javamail which works fine) has not be notified about
those new threee messages.

So, I would like to find a link between the above dovecot message and the
"black-out" which I had, could you help me please?

Thanks, bye

Raffaele Gambelli
WebRainbow? Software Analyst & Developer