Hello @stephdl. Nice to have you back!
Look s like you see the same issue now. The calendar entries are all fine, but the mails are not sent out and the fastest way to verify this - even before you store anything in the calender - is shown in my screen dump on top. Click on 'Teilnehmer' (=Attendees) und you will see the grayed out option to send emails.
Can you see this as described?
I do have the lastest Sogo connector.
1st machine (enterprise edition):
[root@ds1 ~]# rpm -qa |grep -i sogo
[root@dc2 ~]# rpm -qa |grep -i sogo
The question now is why does TB not want to send out mails?
a) because it never does on Caldav calendars?
b) because the initial contact with the Caldav server resulted in a feedback, that the server can not sent out mails (remember there is an option SOGoAppointmentSendEMailNotifications = YES; which is not YES per default!!!)
I vote for option b!
I have once had a situation where the caldav calender took time to sync and during this time I could see that TB was still willing to send out an email (not greyed out option), but after first synchronisation with SOGo the option was greyed out already.
Based on what I have found in the net TB is able to send out mails on caldav calenders, if server is supporting this (also seen on non Sogo servers). I further believe that it is not enough to switch on SOGoAppointmentSendEMailNotifications = YES; to make this happen. See here:
Want to add this information: https://lists.inverse.ca/sogo/arc/users/2014-10/msg00171.html6
and in Sogo Doc page 47 https://sogo.nu/files/docs/SOGo%20Installation%20Guide.pdf6
Sounds to me as some config settings for Sogo are missing and maybe a cronjob, too.