How do you set up a custom fulfillment service in Shopify?

Should your warehouse connect by email or through an app?

Shopify lets you connect a service with an app or set up one that receives orders by email; the email route has one condition:

Once it's active with products assigned, marking an order fulfilled in your Shopify admin sends the service an email with the order details. Unlike app-based services, it doesn't automatically update the order status, so keeping the order up to date falls to you.

How do you add the service and assign products to it?

To activate the service, go to Settings > Shipping and delivery in your Shopify admin, click Add fulfillment service in the Custom order fulfillment section, enter the provider's name and email address, and save. Activating it creates a fulfillment location where you can stock products.

Next, assign products to it so the service can fulfill orders for those products: open each product and, in the Inventory section, select the fulfillment service.

You can stock the same product at both the service's location and your own locations simultaneously, for example to fulfill urgent orders from your own stock while standard orders go through the service.

What if your service needs more than an email?

If your fulfillment service requires more than an email to process orders, Shopify says you can hire a Shopify Partner to develop a custom app that integrates directly with Shopify (see hiring a Shopify developer).

If you no longer want to use the email service, you can delete it; if inventory is assigned to it, you first need to select a new location to inherit the stocked inventory and unfulfilled orders.