Which eComm platform are you using? And what type of email message are you trying to send?

If its Shopify, it might be easier to just pull this data right from that platform. Sort all unfulfilled orders, you could export the data and import it into Klaviyo. 

Hello!

Depending on what ecommerce platform you have integrated with Klaviyo, you can create a segment using the Placed Order and Fulfilled Order variables. In this case, you would want to include any customers who made a purchase during the affected time frame, AND exclude users who have already had an order fulfilled during the same time period (note the AND connector instead of OR).

The segment would look something like this:

You may choose to add additional conditions to this segment, such as “Person is not suppressed for email” and more as you see fit for your use case. 

Hope this helps!

- Ashley Ismailovski