It is your obligation as a seller to provide documentation when you send an item to a buyer.
If the item gets lost during shipment, it is always the seller who has to prove that the item was sent. If you can't show valid documentation, you must compensate the buyer and refund the entire amount for the lost item.
What is valid documentation?
In order to prove that the item was sent, you need valid documentation showing when and to whom the item was sent.
Postnord provides valid documentation if you ship you item as either a registered letter or a Parcel.
Using this postage option, the letter is scanned when you hand it in at the post office and it is trackable all the way to the buyer. Furthermore, the buyer will have to sign for the letter upon receiving it.
All parcels are assigned a tracking number which proves that the item has been sent and where it has been set to. You are able to track where the parcel is located at all times.
We encourage you to sendt the tracking number to the buyer when you've dropped off the package for shipment.
As an alternative to Postnord we recomend DAO or GLS for safe and quick shipment with tracking. Through either of these services, you get a tracking number. With DAO, you and the seller are both notified via text (SMS) and email when the parcel is handed in and when the buyer receives it. This makes the shipment transparent and trackable for everyone involved.
...if you send the item using regular mail, you are not ensured in any way, and you do not have proof of shipment. A receipt for buying stamps or a picture of the package is not valid documentation.
If the item is lost using regular mail, the seller is responsible for compensation. You have to refund the full amount to the buyer including shipping costs, if the buyer paid for that.