How do I limit delivery to the pincodes I actually serve?

Use the Delivery Restrictions plugin.

• On the plugin's Settings tab, turn on Enable pincode restriction. Then add the pincodes you deliver to on the Pincodes tab, one at a time or by bulk import. Any pincode not on the list is blocked.
• A pincode checker appears on the product, cart and checkout pages. Turn on Show delivery estimate to also show delivery days, and Restrict COD by pincode to show where Cash on Delivery isn't available.
• The rules are enforced when the order is placed, so an order to an unserved pincode cannot go through.