for resuming my tests…whatever the client (K9, evolution, thunderbird) when I create an event in the caldav calendar, invitations are not sent to the attendees and I did not see the event in the attendee’s calendar.
But when I delete the event, notification of deletion are sent …fun
I’m not sure where the problem is, probably in sogo but I don’t know why
this problem doesn’t exist when you use the web interface
@others can you reproduce
I have found several statements on the web, where people said that this feature stopped working in TB, when they did an upgrade of their owncloud server. It was then solved on owncloud server itself or it’s configuration.
This of course is a different scenario but proofs, that TB is able to handle this feature! This is a problem on SOGo or SOGo config.
I think a good starting point would be to ask other SOGo users if they have this feature running/usable.
Any idea how we could get in contact with some?
Perfect thanks! I cross my fingers and I’m full of hope 
Thanks for your discussion guys and for effort, I’m afraid that I can’t help you. My knowledge about SOGo is a bit rusty I hope that SOGo devs will reply @stephdl
Update:
Sogo is configured to support “calendar-auto-schedule” (a feature supported over caldav protocol).
When Thunderbird/Lightning is starting up, there is an initial communication with CALDAV Servers to see what they are able to do:
To verify you can:
Based on a buggy implementation in Ligthning things seem to go wrong now. Found this:
Looks like a patch is on it’s way, but that still could take same time.
A workaround would be: Disable ‘calendar-auto-schedule’ feature in SOGo.
Does anyone know how to do it?
Remark:
This does not explain, why other clients suffer from the same problem (evolution or em-client on windows)
no answers on it…BTW @all do you use TB to make appointments or only the sogo webmail ?
My workaround for this nasty bug:
User do have an additional local calender just for event planning. The need to copy a finalized event from local calendar to caldav calender to show other users their complete (shared) calender entries.
At least better than not using the event planning at all.
I’m busy to get in contact with 3 German Universities I know they are sing SOGo since a long time:
An admin from Uni Konstanz confirmed, that this feature is running in Sogo Version 2 ! (still not knowing which version of Thunderbird they use - we will see)
Uni Koblenz is most interesting because they use the latest version.
If anybody does have a contact there pls let me know!
indeed, maybe we could test it with sogo2
isn’t it inside NS 6.8?
yes, it is sogo2 in ns6 
Hello @stephdl I have some news on that topic:
A few days ago there was an update to TB version 52.4 + Lightning 5.4.4. Looks like this started the show again. Together with SOGo 3.2.10 I can send out mails now (the server does it, not TB). On a second Server (Enterprise version with SOGo 3.2.7) it still does not send out. Can you pls cross check if you are able to send out invitation mails now? Thanks!
[lsd@leo ~]$ rpm -qa thunderbird
thunderbird-52.3.0-1.fc26.x86_64
I don’t have your version, when available I will test it
Thanks…
Hello @stephdl, are there any news?
still stuck on the older version
thunderbird x86_64 52.3.0-1.fc26 updates 79 M
sorry i don’t have a window at home to test this version
I also do not have Windows at home. No need, same effect with Thunderbird on Linux. Is there still no update for your Linux version?
I use fedora26, what is your distro ?
I’m on Ubuntu 16.04
I will try to force the update, but still in holidays