I am sorry for my late response. If you really want to purge any EV MSMQ item please follow the instructions from the link http://support.veritas.com/docs/276082. But as I said to you before, it is not a good idea. Because I after you purge Enterprise Vault retrieval service your users might have to restart outlook clients. Definitely there will not be losing of any data but you have to stop Task Controller Service and at that time your EV server will be unavailable for the users. Also from MSMQ you can’t find a users individually.