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The Buyer shipping email that I got in the email sent from eBay is this:
Later, when I make a call to GetSellerTransactions, I get this:
<Street1>1234 test street</Street1>
Which one is correct?
The email is sent as soon as the buyer purchases the item. However, the buyer may not have completed the checkout and so what you see in the email is the primary (default) shipping address. If the buyer chooses a different shipping address during checkout, then the address that you see in the API response will be different from the email.
Note: Even with the API, you should use the buyer's shipping address only if the checkout is complete. Look for the field CheckoutStatus - if the value is CheckoutComplete, then you read the other information such as the buyer's shipping address, shipping service selected etc. If the value is anything other than CheckoutComplete, the buyer has not completed the checkout process and the values that you get in the API response are also defaults, which can change.