I have a user that started reporting duplicate appointment in Outlook calendar we where still in 15.x version. The user have outlook 2016 using IMAP e has calender synck with smartermail.

Now whe are at 16.3.6508, user continues with duplicated itens in calendar plus after upgrading from 15.x to the actual version i verified that the calender is not sincronizing any appointment with smarter mail and an issue that came from other version like 15.x continued.

Apointments created in calendar from webmail does not synck the reminder value to outlook . 

The same problem happens when creating the appointment in Outlook calendar the reminder value doesnt show up in calender in webmail.