@Tlek Aipov (Akvelon INC) Thank you for reaching out to Microsoft Q&A. I understand that your client is having challenges with the Delete message API as it requires the pop receipt property in order to delete messages currently.
I checked regarding this with the PM for this service and confirmed that with respect to Delete behavior, it has always been this way i.e., it had always required the most recent pop receipt and that things haven't changed recently. This feature is to make sure that the customer does not delete a message that they didn't pull. Hope this helps.
Please let us know if you have any more questions and we will be glad to assist you further. Thank you!
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