If you're getting RSVP via forms, then try out AMP email forms. The recipient can fill out the form within the email through AMP without any redirects. As most of the drop-off occurs due to redirects,
AMP email forms eliminate that friction by bringing web-like functionality within the email. So, recipients get a hassle-free experience, and you get higher RSVPs on your event emails.
Learn more: What is AMP for Email - Use Cases, Benefits, Examples, and Components