When you receive the response back from Google in your test, the event status won't get automatically updated.

Are you able, from SOGo's webmail interface, to read that mail and update the participant status?

yes, also from thunderbird with plugin.
and yes the status should be parsed when receiving the response, which works with a local calender

So there's no SOGo bug.

SOGo cannot parse automagically the received email - it doesn't have user's passwords to read their emails.

i do understand that sogo cannot parse it automagically.

current setup is: apple calender with sogo-account, apple mail configured.
when sending an invitation from apple calender and getting back the response in apple mail, we click on that mail and have .ics attachments.
even explicitly clicking on that attachment, it does not update attendee status (but calender acknowledges the event by popping up the same event)

SOGo cannot do anything about this.

i will do more tests with other DAV-servers. i then guess apple's implementation is the culprit here.
thank you

sorry for reopen but i thought on your words
"SOGo cannot parse automagically the received email - it doesn't have user's passwords to read their emails."

and it left me puzzled:
i assumed that the whole purpose of the middleware SOGo is to be a proxy for mail and a store for calendar
as well as addressdata. Every account there is, has an IMAP account attached to get invitations from
external users and has a globally configured SMTP to send invitations.
On every receipt of a mail, the content is parsed (my assumption) at least by SOGo and Thunderbird with Plugins.
In Case of a match in terms of event-IDs or some other matching parameter, the event gets updates!?
is that wrong?

then how is parsing of calendar-data done when not via mail with ics-attachment?

SOGo is no email proxy.
To be a proxy would mean, that every email of all users in SOGo would pass through SOGo.
That is not the case.
SOGo is an email frontend, which means, it only has access to the users emails per IMAP, as long as the user is logged into the webfrontend of SOGo.

It parses an email the moment you open it for reading in the webfrontend.
Only then it can see, that this specific email is an event reply.
And only then it can update your event.

i see. thanks!