This worked for me, tested via Postman and even with the Python Fuel SDK
<?xml version="1.0" encoding="UTF-8"?>
<s:Envelope xmlns:s="http://www.w3.org/2003/05/soap-envelope" xmlns:a="http://schemas.xmlsoap.org/ws/2004/08/addressing" xmlns:u="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd"> <s:Header> <a:Action s:mustUnderstand="1">Retrieve</a:Action> <a:To s:mustUnderstand="1">https://{{et_subdomain}}.soap.marketingcloudapis.com/Service.asmx</a:To> {{dne_etAccessToken}} </s:Header> <s:Body xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> DataExtension ObjectID CustomerKey CategoryID Name IsSendable SendableSubscriberField.Name CategoryID equals 288044 </s:Body> </s:Envelope>