Hello Zimbra Community.

I've got an interesting one, that I haven't been able to nut out.

Using the ZCO 5.0.18 with Oulook 2010 32 bit, the Outlook Client is getting a Synchronisation Failure.
When looking at the report it says "Unknown failure".

Mail is still getting downloaded, and is matching with the server, but any changes made in the client (such as deleting mail, or moving to other folders) are not being pushed to the server.

This also goes for Calendar events.

The mail client can successfully send mail.

I tried the steps listed in Outlook Troubleshooting Options - Zimbra :: Wiki but didn't acheive a whole lot - repairing the ZCS Client did nothing, disabling addons (of which there were only the Microsoft defaults) did nothing, looking for possible firewall issues with Anti-Spam programs client side raised nothing.

I enabled logging, and interestingly enough when I was logging Verbose with Calendar logging, the Outlook client would fail to start - crash after selecting the Zimbra mail profile. There was no error- only a generic failure.
I turned off verbose logging and calendar logging and it started and generated logs. There are statements in the logs that the client is failing to sync but I couldn't make heads nor tails of the cause. I have attached the logs - ctrl+f for failure yields those results.

I have a gut feeling based on the errors with the logging that is is an issue with the calendar, but couldn't fond anything conclusive.
I did also attempt to check for anything extra, such as categories/tags that had strange naming conventions but the client only has the default Microsoft categories (red, blue etc) configured.

Any additional ideas would be appreciated - I'd rather not delete the zDB and re-install the ZCS if I can avoid it, as it's a large mailbox, and would take some time to download on the external site.

Looking forward to your replies If I can provide any additional information, let me know. I have attached a zip of the log files.