I have ZCS 8.8 on Ubuntu 16.04, serving some 3000 email accounts.
Mostly there's no problem and everything is working fine...
...except rare, but very disturbing annoyances, which I do not have idea how to approach:
- Sometimes descriptions vanish from calendar event. All remember they were there, but next day...gone. Just calendar event with TITLE, but BODY is empty.
- Sometimes mail attachments vanish. User remembers there were, for example, 3 attachments, and indeed sender says 3 were sent, but now only 1 is attached to mail.
- Maybe not related...Outlook IMAP sync works just fine for 1 week, then it begins striking for a day or two (user needs to either click Send/Receive button, or click to other mail account then back to refresh Inbox in Outlook). After few days all works fine again, without restarting Outlook or server.
What I might have suspected it network/server load or even TLS connection breaking, but I do not have enough evidence on this. Server is generally not overloaded, usually creeping between 5 and 10% CPU load.
Any idea what to check, look for, debug?