Historically, we have had big problems with sync failures in Outlook. Users are therefore rather tired of having to change (lower) the synctoken on a function that is supposed to work flawlessly. Not to mention the worry of not knowing when Outlook stops receiving email after a sync failure occurs.
ZCO for Zimbra 9.0.0 Patch 28 fixed ZBUG-2984 (Intermittently, Outlook would not sync emails with large metadata.) has reduced the problem a lot, but not eliminated it. We are still getting sync errors in ZCO that seem to be related to various calendar events such as invitations, reminders, etc.
Does anyone else share this experience with ZCO and Outlook 365?