Post Offices in Sunnyside, Washington, United States SearchSearch SearchSearch View: Grid 1View: Grid 2View: Grid 3View: Grid 4View: Grid 5View: List Sunnyside Post Office No Reviews Favorite Fax: (509) 837-2557Phone: (509) 837-4875Retail Hours Sunnyside Carrier Annex Post Office No Reviews Favorite Fax: (651) 456-6272Phone: (509) 837-8165Retail Hours