Restricting the scope of "success" notifications

[Tomas Macek]

Hello, our system is sometimes under attack of spammers using 
"NOTIFY=SUCCESS" param in "rcpt to: " header. And because of a random From 
address, the DSN message obviously goes to an nonexistent server 
or user.

I've read the "Restricting the scope of "success" notifications" topic at 
http://www.postfix.org/DSN_README.html#scope and I'd like to ask you about 
some details:

1) if I turn off the DSN for the networks outside of $mynetwork, do I 
understand it well, that we will not send them (to the outside world) any 
more DSNs with "user over quota" or "access denied"?
We won't be sending anything probably in that case, just asking to be 
sure.

2) how much is it normal to turn off the DSN for outside world? What is 
your settings?

Regards
Tomas