Bounce Attack and InBound filtering only

I've a problem of Bounce Attack with a lot of NDR email messaging arriving and being delivered.

I'd like to use this solution www.symantec.com/docs/HOWTO53629 but I think that it only works if we use SMG with OutBound Filtering features, is that correct?

At the moment we're in the following situation, so I think that is not appliable...

Do I need to put the SMG in "Inbound and outbound mail filtering" in order to achieve the desired result?

Thanks!