[horde] Edit event conflict with Active Sync and Outlook 2013

[Bjoern Voigt]

If I add a new calendar event in Outlook 2013 to my Horde calendar,
open the event again and change something (subject, location etc.) I
get the following message:

    The item cannot be saved because it was changed by another user
    or in another window. Do you want to make a copy in the default
    folder for the item?

The Outlook error message is wrong, because only one user (me) added
and edited the event in one program (Outlook). If I edit the event a
second or third time, the error message does not appear again.

Is this a known Horde Active Sync error or a typical Outlook error?
Is there a work-around?

The following KB article suggests to change the conflict resolution
settings in Outlook. The article is not specific to Horde.

    Automatic conflict resolution handling is enhanced in Outlook 2010
    https://support.microsoft.com/de-de/kb/2755373/

Greetings,
Björn