spammers

ok a bit of advice.

now I have a spam program, which work great, but its a real pain having to sort through, wots real and wots not so a few questions

1> when somone sends me a mail, does the spammer know I've got it ? - as long as I dont reply, in other words is there some kinda of mechanism, where as if the spammer does not get a failed message he knows its a worker ?

2> can I simulate a "failed mailer deamon" reply, so the spammer thinks the address he's reached is dead ?
i.e can I send a reply, back to the spammer, like "invalid address" etc, or will the fact he's had a reply proove this is a worker

cheers

Jay