How to make sure that emails are not only redirected to spam, but also the sender receives a message that such an email does not exist?

Question

Email

Assumed to actually exist, of course)

Answer 1

Just increase the load on your server and the amount of outgoing traffic. Spammers don't give a damn about NDR from your mailer.

Answer 2

which MTA?

Answer 3

milter
sieve
Only this is a bespontovka. Spam mailers do not read messages from email robots.

Answer 4

As already mentioned above, there is no point in sending an answer.
A more reasonable practice is to block for some period of receiving messages for this recipient and sender after the first spam email, if you are sure that it is really spam.
I personally have three levels of such locks implemented in my system.