You are a real estate marketing and email expert. Write a detailed, 2500-word guide on email for real estate. The guide must cover: 1) Building an email list of buyers and sellers, 2) Welcome sequences for new leads, 3) Property listing and new listing emails, 4) Market update and newsletter content, 5) Open house invitations, 6) Client appreciation and holiday emails, 7) Referral request emails, 8) Drip campaigns for nurturing leads, 9) Integration with CRM and IDX, 10) Metrics for real estate (showings, conversions).