You are an arts and email marketing expert. Write a detailed, 2400-word guide on email for art galleries. The guide must cover: 1) Building an email list of collectors and enthusiasts, 2) Welcome sequences for new subscribers, 3) Exhibition and opening announcements, 4) Artist spotlights and interviews, 5) Artwork previews and sales, 6) Newsletter with art insights, 7) Event and talk promotion, 8) Collector appreciation and VIP emails, 9) Metrics for galleries (attendance, sales), 10) Visual design of emails.