Post Offices in Manassas, Virginia, United States SearchSearch SearchSearch View: Grid 1View: Grid 2View: Grid 3View: Grid 4View: Grid 5View: List Downtown Manassas Post Office No Reviews Favorite Phone: (703) 392-3765Retail Hours Manassas Post Office No Reviews Favorite Fax: (703) 361-4708Phone: (703) 368-2146Retail Hours Manassas Annex Post Office No Reviews Favorite Fax: (703) 368-9213Phone: (703) 369-0227Retail Hours