If you want to accept the invitation, reply directly on the RSVP page using a form.
Anyone who wants to come, answers directly on the form. The owner of the rsvp site has options to limit the circle of invitees. The advantage of the rsvp site is that the transmission of data is protected - this is already specified by the new RSVP-Domain of Google.
Hans-Peter Oswald
https://www.domainregistry.de/... (English)
https://www.domainregistry.de/... (deutsch)
https://www.domainregistry.de/...
https://www.domainregistry.de/...