PigeonTrail for Shopify
PigeonTrail tracks the orders you mail with a stamp. Your open, paid orders come in straight from your store, and you print their envelopes with a USPS barcode on each one. When a letter prints, PigeonTrail marks its order fulfilled in Shopify with a tracking link, so your buyer gets that link in Shopify's own shipping email.
First sign in to PigeonTrail with your email, which needs no card, and then connect your store from Settings. Your first 100 letters each month are free.
What the app does
The app imports your paid, unfulfilled orders that ship to a US address, checks each address against USPS data, and prints envelopes or labels with the USPS Intelligent Mail barcode on them. When you print, it fulfills the order in Shopify with the tracking number and a link to your buyer's tracking page.
PigeonTrail only reads your orders and writes fulfillments, so it never changes your products, prices or customers. You can disconnect it any time from Settings, or by uninstalling the app in Shopify.