'Return the connection to the Authenticate state.
This command is allowed in the Selected state.
Issuing this command will perform the same actions as issuing the
close command, but will also generate an \'expunge\' response for
every message deleted.
@rtype: C{Deferred}
@return: A deferred whose callback is invoked with a list of the
\'expunge\' responses when this command is successful or whose errback
is invoked otherwise.'

def expunge(self):

    cmd = 'EXPUNGE'
    resp = ('EXPUNGE',)
    d = self.sendCommand(Command(cmd, wantResponse=resp))
    d.addCallback(self.__cbExpunge)
    return d
