The email informing the first shipping update is not sent until the API returns the second shipping update, which must be different from the first one.

1. On the VTEX platform, create an order and follow the usual order flow to the status Invoiced.
2. Send a shipping update for the order via the Order tracking API.
3. Note that the first shipping update email is not sent.
4. Send another shipping update identical to the first one.
5. Note that the first shipping update email is not sent.
6. Create another order and follow the usual order flow to the status Invoiced.
7. Send a shipping update for that order via the Order tracking API.
8. Note that the first shipping update email is not sent.
9. Send another shipping update that is different from the first one.
10. Note that the first shipping update email has been sent.

As a workaround, ensure that the second update sent via the Order tracking API is different from the first one. By doing so, the email will be sent.