You can use the delete fetch action to delete messages from the Exchange repository. You cannot use the action to delete folders or mailboxes.
The delete action accepts a comma-separated list of document identifiers. Specify the identifiers for the documents that you want to delete:
http://host:port/action=Fetch&FetchAction=Delete
&Identifiers=Identifier_CSV
For more information about using the delete fetch action, refer to the Exchange Web Service Connector Reference.