It is not always necessary to create a product mapping, sometimes you can also use the content already known to the marketplace. For example, the marketplace may match your EAN code to an existing product.
In the case of bol.com, you can hitch a ride on the content that already exists. The same applies to Amazon, Blokker, and many other channels. For some channels, it is needed that you always provide product information (by means of mapping groups). For example channels like Beslist.nl, fonQ and HomeDeco.
Good to know: if you are selling products that already exist on a marketplace, and you have disabled product synchronization or created no mapping groups, the product information will remain as it is. No changes to the product information will be passed on.
Our advice?
Always create a mapping group when you have the right product information. Not only will this ensure that new (unknown) products will come online, but also that product information will be enriched from the products on the marketplace.
Are you not sure if you can use existing products from a marketplace, to add your own offer? Contact the marketplace and ask them how it works. In some cases, marketplaces do or don't accept product information. They can give you the best advice you can get.