Duplicate Shipping Update emails being sent

[garrett_s]

We've written an app that allows users to have orders fulfilled by a third party. And we update the fulfillment for the first-party user with the third party's tracking number. 

We have an issue where the customer gets duplicate Shipping Update emails. When the product gets delivered, the customer gets a Shipping Update emails and a Shipping Delivered email immediately after. Like below:

We would like only the Shipping Delivered email to be sent. 

It seems like every time we call the Update_fulfillment API, Shopify sends a Shipping Update email. Even if the tracking number associated with the fulfillment does not change. 

Is there anything we can do to prevent this from happening? We don't want our customers to receive confusing, duplicate emails.