OL2019/2021 calendar problem: my multitenant login name appears in required attendees list

[jacsa]

Hello Everybody,

I have the latest community edition (core: 11.0.2, z-push 2.6.4), configured in multitenant mode. The clients are Outlook 2021 and 2019 connected with ActiveSync.

My user name is jacsa, company name is jn => user name is jacsa.jn.

In OL2019 or 2021 calendar I create a new meeting and invite an attendant whos e-mail address is jacsa12@gmail.com . He accepts the meeting request.
Then I open the meeting in outlook to send an update, but I notice my user name as required attendant. It resolves to an invalid e-mail address (jacsa.jn@kopano.jacsa.net), so I receive a delivery failure mail message when I send the update out. My user name also appears in tracking page.

I also see my user name as required attendant on my iPhone.
Deskapp/webapp does not produce this weird symptom.
I suppose that z-push inserts the extra data into required attendant e-mail address list.

Does anybody have an idea how to cure this problem?

Thanks,
Janos