3183741 - Error: "PO-11: Cannot deliver order. Terminal error code for PO status" when sending Purchase Order (PO) via email

PO is failing and not reaching the supplier email. The History tab for the PO shows the error:

PO-11: Cannot deliver order. Terminal error code for PO status: The state of document XXXXXXXXXXXXXXXXXXXXXXXXXX was changed to Failed after unsuccessful attempts to resend it.

The supplier is able to view the PO in their Inbox, but it is marked as Failed. In the PO History tab, the error PO-3: Cannot send order to supplier is displayed for the order.

The Stacktrace column in the PO History tab shows the exception:

com.webobjects.foundation.NSValidation$ValidationException: The emailAddress property of ANEmailTracker is not allowed to be null. (...)

Additionally, in both buyer and supplier accounts, it is possible to see Transfer to the next integration point has been delayed. Retries: X in the History tab of the PO, shown several times.

The emailAddress property of ANEmailTracker is not allowed to be null, po failed, order failed, po failing, order failing, purchase order, order failure, PO-11: Cannot deliver order, Failed after unsuccessful attempts to resend it, Terminal error code for PO status , KBA , SBN-AN-TX-POA , Transaction (Purchase Orders, Ship Notices & Goods Receipts) , Problem