Shipping Between APO/FPO/DPO Addresses
The short answer
Mail between military addresses — including FPO to FPO, ship to ship — is domestic U.S. mail at domestic prices, in both directions. Letters and documents under 16 ounces need nothing special. Packages need a computer-generated customs form even between two military addresses, some ZIPs restrict contents, there is no Priority Mail Express between military addresses, and ship-to-ship delivery can take 3-6 weeks or more.
Domestic Rates, Both Directions
Every APO/FPO/DPO is legally a branch of a U.S. post office (DMM 703.2.1.1), so military-to-military mail is domestic: normal First-Class, Ground Advantage, or Priority Mail postage, no international fees. The military-only Priority Mail APO/FPO Large Flat Rate Box is priced below the regular domestic large flat-rate box, and the boxes are free from The Postal Store.
The Customs-Form Rule People Miss
USPS's customs rule reads "to or from" any military post office and applies BETWEEN them too. Letters, cards, and documents under 16 oz: no form. Anything containing goods (any weight), or any item 16 oz and over: PS Form 2976 or 2976-A required — and since July 14, 2024 the form must be computer-generated with electronically transmitted customs data; handwritten forms are non-compliant and screened for. At a retail window you fill out worksheet PS Form 2976-R and the clerk generates the official form.
Restrictions Are Per-ZIP
USPS republishes the full military-ZIP restriction table every two weeks in the Postal Bulletin, as letter codes per ZIP. Shore FPO/APO ZIPs import host-nation rules (commonly: no alcohol, no pork products in some countries, no firearms). Ship FPO ZIPs carry almost no content restrictions — typically just the customs-form code and no-express — because the destination is a U.S. vessel. Our Military Mail Restriction Lookup tool at /tools/military-mail-restrictions covers all current ZIPs. Vapes and e-cigarettes are nonmailable to, from, or between all military addresses with no exceptions (USPS final rule, Oct 2021); cigarettes and smokeless tobacco likewise.
No Express Option Between Military Addresses
Priority Mail Express Military Service is not available between APO/FPO/DPO addresses (DMM 703.2.9.3). The fastest available is Priority Mail; Parcel Airlift (PAL) is capped at 30 lb / 60 inches combined.
Ship Mail Is Hostage to Ship Movement
Outbound mail leaves a ship at port calls or by air; it flows through Fleet Mail Centers. Inbound ship mail is HELD at the servicing Fleet Mail Center under the ship's routing instructions and delivered at the next port call, carrier onboard delivery flight, or underway replenishment. Ship-to-ship mail therefore crosses two fleet-mail legs and waits on two ships' schedules: shore-to-shore commonly runs 1-2 weeks; anything involving an underway ship commonly runs 3-6 weeks and can exceed two months. No published service standard exists for delivery aboard a ship.
Address Format
Domestic format only: name; ship or unit name; unit number + box number; FPO (or APO/DPO) with "state" AA, AE, or AP; 5-digit ZIP. Never include a city or foreign country name — that diverts the piece into the international network. "Any Service Member" mail is not accepted.
Sources
- 39 U.S.C./DMM 703.2 (military mail is domestic; pe.usps.com/text/dmm300/703.htm)
- Postal Bulletin 22699 (2026), Overseas Military/Diplomatic Mail table + restriction legend
- USPS.com "Ship to an APO/FPO/DPO" (usps.com/ship/apo-fpo-dpo.htm)
- Federal Register 2021-22787 (Oct 21, 2021 — ENDS nonmailable; no military-mail exceptions)
- Postal Bulletin 22652 (Jul 2024 — computer-generated customs forms required)
Last Verified
Facts verified against USPS sources August 17, 2026. Rates and per-ZIP restrictions change — check usps.com and the current Postal Bulletin before mailing.