[SalesForce] How to Delete Subscribers From All Subscribers list

Pretty sure you can't delete all subscribers on the All Subscribers list all at once. If it was another list, you can delete the List Object, which will delete all of the subscribers in it.

Here's a sample SOAP envelope.

<?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">Delete</a:Action>
      <a:MessageID>urn:uuid:cec6826f-1ac3-4559-934b-a5ad8e081c3c</a:MessageID>
      <a:ReplyTo>
         <a:Address>http://schemas.xmlsoap.org/ws/2004/08/addressing/role/anonymous</a:Address>
      </a:ReplyTo>
      <a:To s:mustUnderstand="1">https://webservice.s4.exacttarget.com/Service.asmx</a:To>
      <o:Security xmlns:o="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd" s:mustUnderstand="1">
         <u:Timestamp u:Id="_0">
            <u:Created>2015-01-30T15:29:13.355Z</u:Created>
            <u:Expires>2015-01-30T15:34:13.355Z</u:Expires>
         </u:Timestamp>
         <o:UsernameToken u:Id="uuid-3bd5c867-ef2e-4768-a5e7-3a119b1a8765-11">
            <o:Username><!-- Removed--></o:Username>
            <o:Password><!-- Removed--></o:Password>
         </o:UsernameToken>
      </o:Security>
   </s:Header>
   <s:Body xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
      <DeleteRequest xmlns="http://exacttarget.com/wsdl/partnerAPI">
         <Options>
            <SaveOptions />
         </Options>
         <Objects xsi:type="List">
            <PartnerKey xsi:nil="true" />
            <ObjectID xsi:nil="true" />
            <CustomerKey>aspriggs-test-list</CustomerKey>
         </Objects>
      </DeleteRequest>
   </s:Body>
</s:Envelope>

After a month long tussle with Marketing Cloud Support, I was finally able to resolve this.

Our current set up is an Enterprise 2.0 account. The recommended method was to export the All Subscriber List to a list and delete the list, while check the option to delete this from all applications.

Problem is that although the UI gives you the option to do this, it is a bug. You cannot delete the All Subscriber List from the Business Unit Level.

I had to switch to the enterprise level and import the All Subscriber List here to delete it.