We now run our Zimbra server about a year and are very happy with it.
The only thing is, sometimes, all user got logged out and cannot login for about 10 minutes. Every login try will be answered with "Password wrong". Even the back-end login fails.
I had a look at the logs at /opt/zimbra/logs, but couldn't really find any hint. I also tried to just restart Zimbra nor the whole server, but no luck.
Maybe someone has a tip where to look? All daemon seems to run without issue.