@morrow without logs this will be hard to track down. can you ask your administrator to open up a support case for this?
Problem: I just updated Zarafa to a new version and now I get reminders that I didn't ask for.
Solution: Outlook has a table for all reminders.This table will be completed during the update with reminder information for all possible calendar items with a reminder. Old reminders will be (re-)activated and are hard to remove.
To remove these old reminders, close Outlook and perform the following steps: Click on Start > Run and enter: outlook.exe /cleanreminders. Then click OK to start Outlook. During start-up, Outlook will clean the reminder table.
If reminders do not work at all after this command, you will need to close Outlook again, and perform the following steps:Click on Start > Run and enter: outlook.exe /resetfolders. Then, click OK to start Outlook. After this step, your reminders should work as expected.