No email notification to invitees in calenders

I have basic problems with calender event invite notifications.

  • nextcloud 13.0.0
  • email via SMTP, successfully tested
  • calDAV account in Apple calender

Invitees get no notification about invitations, neither in shared calenders nor in personal calenders. E-Mail notifications work without problems.

Should the invitations send by my local Apple Calender or by the Nextcloud server installation?

solved by magic: I don´t know why, but it works now like a charme without changing anything.