Unable to send email invitation to Calendar Attendees

I’m relatively new to Nextcloud and for the past year used it primary as file share.
I have created calendar and shared with certain users thus creating groups.

Primary issue, when creating an event and adding external users emails to be sent invitations to, system fails to send those email. What might be the issue?

I’m running nextcloud 18.

Is the calendar shared with you? Only calendars for which you are the owner can allow sending invitations.


Also you need to make sure it’s activated in Nextcloud’s settings, section groupware (URL is /settings/admin/groupware).