I noticed the following, I don't know if it's a bug in the new version 4.x.x of a feature that has been disabled:

I had zimbra 3.1.4 working, calendar was working ok with reminder working well too. Since I upgraded to 4.x.x (I've now 4.0.2, but it was happening in 4.0.1 too), when a user logins to the webui the appointment reminder that was usual to pop up warning when some calendar event overdues or is coming, simply is gone. It only shows up if the user goes to the calendar and click on "refresh". After refresh it works well until the user logout. Can I do something to try fix this? Looks like something missing on user login that tells to make calendar refresh.. It happens on all users I have.