This is not a duplicate to 0006002: We don't use LDAP and the effect is that the organizer is an alias, where the actual organizer is member of. I can specify more clearly: The clear name of the organizer varies between all members of the alias group.

I also checked whether or not the setting of the parameter SOGoDefaultCalendar does make any change: It does not...

...we meanwhile upgraded to version 5.12.0 - no improvement.

I furthermore experienced an effect where - for the identical UID of a calendar entry the EMAIL for the ORGANIZER varies between the attendees. E.g. an SQL-query for a distinct UID and two attendees demonstrates this effect:

select c_content from sogo_store where c_name = '<UID of the record>.ics';

Result: 2 records (which is fine) and the record belonging to the real organizer reads:

ORGANIZER;CN=Linda Engel;EMAIL=GF@nova-institut.de:mailto:linda.engel@nova-
institut.de

...and the record of the attendee reads:

ORGANIZER;CN=Linda Engel;EMAIL=linda.engel@nova-institut.de:mailto:linda.en
gel@nova-institut.de

The email-address "GF@nova-institut.de" is an alias where linda.engel@nova-institut.de is member of.
Any hint for further analysis or to resolve this issue is gently appreciated.

Hello,
In this example, how was created the event? From webmail sogo or from a client?
Also, how did you define your user aliases?

It was created by Apple Calendar and all aliases are defined using the mailcow-API.

Apple Calendar with caldav or Activesync?
I'm not very familiar with mailcow, can you tell me the api endpoint you uses?

We only use CalDAV, no ActiveSync.
The API-endpoint is: https://mailcow.host/api/v1/add/alias
The complete API description can be found here: https://mailcow.docs.apiary.io/#reference
...and for aliases: https://mailcow.docs.apiary.io/#reference/aliases

I really would like to track the CalDAV related messages, from requesting information about users (myself and possible invitees), availability and possibly more related stuff as well as the payload of GET and POST messages that are sent and received between the backend and the Apple Calendar Client.
Is there any documentation that guides me?