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There are a couple of postal codes that are within other postal codes, and those are okay if swapped.
Check the tracking. Does it show delivery to the postal code on your label receipt?
Sometimes, a seller, sending multiple items, may enter the wrong tracking number into an order.
If the tracking number is correct, and it shows delivery to the postal code used at checkout and on the buyer's order, you should be covered.
In some cases, a buyer account may have been compromised (or the buyer moved and forgot to update) so that the shipping address is not that of the buyer. Nonetheless, those scenarios are not your responsibility.
You could ask the buyer to check their purchase history to confirm the shipping address shown on the purchase is the one they had expected. If not, they need to fix their account and the loss is theirs.
I had a recent situation as a buyer. The seller shipped UPS and tracking showed delivery to a different town. My first suspicion was the tracking number scam (using the tracking number of some other shipment), but the seller did not seem shady. So I called my local UPS center and asked if the "Delivered" scan matched the address associated with the tracking number. It did not. The driver misdelivered two packages with a third that was correctly delivered. Since UPS could not recover the misdelivery, I contacted the seller to open a UPS claim (which only the seller can do in the case of UPS). And I opened an eBay claim for item not arriving - which the seller closed with a refund.
As a seller, you should be able to perform a similar trace, if necessary, since a seller is responsible for delivery to the address used at checkout.
