Letter Pack Light is intended for mailbox delivery, but fitting the 3 cm mailing limit does not guarantee that it will fit the recipient’s mailbox. Japan Post’s current Japanese service page says that, when it cannot be placed in the mailbox, delivery staff try face-to-face delivery; if the recipient is absent, they leave a non-delivery notice and take it back to the delivery post office. The English conditions page summarizes the fallback as a notice and return to that office without describing the face-to-face attempt. Plan for a notice and collection or redelivery rather than promising one particular doorstep outcome. Japan Post: Letter Pack service conditions in Japanese
This guide is desk research from Japan Post’s published rules. It does not describe a parcel we mailed or a delivery we observed.
The 3 cm test is at the sending end
Japan Post says Letter Pack Light accepts contents up to 3 cm thick and 4 kg, using its dedicated A4-file-size envelope. Those limits decide whether the finished item may be sent as Light. They do not measure the recipient’s mail slot, the free space inside the box, or whether the box is already full. Japan Post: Letter Pack Light size and weight
That gives two separate questions:
| Question | What to check |
|---|---|
| Can I post it as Letter Pack Light? | The sealed envelope’s thickness, weight and permitted contents. |
| Will it be deposited at the address? | The destination mailbox’s usable opening and space, which the sender may not know. |
A hypothetical example makes the distinction clear. A document bundle sealed to 2.5 cm may pass the Light thickness limit. If the destination has a narrow slot or a full mailbox, the delivery method can still change. This is an illustrative scenario, not a claim about the dimensions of Japanese apartment mailboxes.
What if the box is too small?
The current Japanese Letter Pack page says staff attempt face-to-face delivery before leaving a notice when the recipient is absent. The English Letter Pack conditions state that an item that does not fit is taken back with a notice. The pages differ in how much of the intermediate step they describe, so the dependable conclusion is narrower: mailbox delivery is not assured, and the recipient may need to act on a notice. Neither page promises that a sender can nominate face-to-face delivery while paying for Light.
If the recipient will be away, tell them the tracking number and ask them to watch for a notice. Japan Post says it records acceptance and delivery completion for Letter Pack tracking. A tracking event should be read as the event reported, not as proof that the item went through the mailbox. Japan Post: service overview and tracking
When to choose Plus instead
Choose Letter Pack Plus when face-to-face handover with a receipt seal or signature is the requirement from the start. Plus is described as a face-to-face service; Light is a mailbox service with a fallback if the box cannot take the item. Plus also has no 3 cm thickness limit as long as the dedicated envelope can be properly closed and the 4 kg limit is met. Japan Post: Letter Pack Plus and Light
At the source check date, Japan Post lists Light at ¥430 and Plus at ¥600, a difference of ¥170. That difference buys a different planned delivery method, not a guarantee that the recipient will be home. Check the current Japan Post service page before mailing, because prices can change.
Both versions lack compensation for loss or damage under Japan Post’s Letter Pack conditions. If the contents are fragile, valuable or difficult to replace, choose a service based on those needs instead of treating a receipt signature as insurance. Japan Post: Letter Pack limitations
First-party sources checked
Related guides
Compare services for A4 documents and what to do with a redelivery notice.