ICS file altered

[StarHopper27]

My issue

ICS files are being unexpectedly modified during transmission when sent via Z-Push and ActiveSync in my setup. I am using Z-Push, ActiveSync, and Kopano.

The problem seems specific to Z-Push, as ICS files sent directly from Kopano (without Z-Push) remain unchanged. However, when I send ICS files via Z-Push/ActiveSync (e.g., from Outlook through Z-Push to Kopano), the ICS files are altered. Fields like PRODID and additional X-MICROSOFT-CDO-* properties are added, and Gmail fails to correctly process these modified ICS files.

My ICS file before:
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//My Calendar App//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
UID:[email protected]
DTSTAMP:20250122T130000Z
DTSTART:20250123T090000Z
DTEND:20250123T100000Z
SUMMARY:Meeting with Team
DESCRIPTION:Discussion about the upcoming project launch.
LOCATION:Office Meeting Room
STATUS:CONFIRMED
SEQUENCE:0
END:VEVENT
END:VCALENDAR

And following how the ICS file looks after being processed by Z-Push:

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Kopano//11.0.2//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
TRANSP:OPAQUE
X-MICROSOFT-CDO-INTENDEDSTATUS:BUSY
CREATED:20250122T152703Z
LAST-MODIFIED:20250122T152703Z
DTSTAMP:20250122T152703Z
DTSTART:20250123T090000Z
DTEND:20250123T100000Z
SUMMARY:Meeting with Team
LOCATION:Office Meeting Room
DESCRIPTION:Discussion about the upcoming project launch.
CLASS:PUBLIC
UID:[email protected]
SEQUENCE:0
X-MICROSOFT-CDO-OWNER-CRITICAL-CHANGE:20250122T152703Z
X-MICROSOFT-CDO-ATTENDEE-CRITICAL-CHANGE:20250122T152703Z
X-MICROSOFT-CDO-APPT-SEQUENCE:0
X-MICROSOFT-CDO-OWNERAPPTID:-1
X-MICROSOFT-CDO-ALLDAYEVENT:FALSE
END:VEVENT
END:VCALENDAR

Steps to reproduce the behavior:

Generate an ICS file programmatically or in Outlook and send it via Z-Push/ActiveSync to a Gmail recipient.
Inspect the received ICS file in Gmail or another email client.
Observe that the ICS file has been modified, and Gmail is unable to process the calendar event correctly.
Expected behavior
The ICS file should remain unaltered during transmission via Z-Push/ActiveSync, and Gmail (or other clients) should be able to parse and use the calendar event without issues.

The interesting thing for me: when I send the email with the ICS file to an Outlook recipient, it goes through without any modifications. I'm a bit at a loss and would appreciate any help. Is there perhaps a setting in Z-Push that optimizes the ICS file specifically for Outlook?
I am looking for guidance on how to prevent Z-Push from modifying ICS files so that they remain intact and compatible with all clients, including Gmail.

[matidau]

This looks to be a problem on the Kopano side or Outlook. Z-Push does not add in these properties to an ics.

You may need to investigate the Kopano code base and come up with your own fix as there is no longer any support for the product outside the SaaS version, from what I understand.

Alternatively you could reach out to Gmail support as these are documented fields and perhaps Gmail is not parsing them correctly.

[StarHopper27]

Thank you matidau, for your quick answer then 👍