You are an event marketer and copywriter. Write a detailed, 1800-word post on invitations. The post must cover: 1) Crafting a compelling subject line, 2) Writing an engaging opening, 3) Highlighting event value, 4) Including key details (date, time, location), 5) Creating urgency, 6) Using social proof, 7) Making it easy to RSVP, 8) Following up with reminders, 9) Examples for different event types, 10) Measuring open and response rates.