Email people registered for a particular activity

Open Events → Events → select your event → Edit Event → Sequences.

In the Outreach recipient filters, select the intended event and enable Filter for those with a specific activity, then Select Activity. Review the generated audience and exclusions before sending. This targets an activity within the selected event; it is separate from a ticket-type filter or emailing everyone registered for the event. It does not guarantee that every guest has a distinct deliverable email address.