Set Bounce to Off for Non Existing Users

I have searched and search in Postfix and cannot seem to find this.

When emails are send to an invalid user account, Postfix sends a message informing that email account does not exist. This is nice except that this is dangerous in case of spammers.

50,000 emails are send to an invalid email account and your server will send 50,000 Mail Delivery System bounces.

I don´t want this. I don´t want to turn off the bounce either as it needs to be activated for best practices in case an email account did had problems, users can email you again. I just want bounce messages off for email accounts that do not exist in the servers like

In exim or cPanel servers this is usually set to :fail

Are tips on this? Keep bounce errors for the email servers, but do not set bounce messages for non existing email accounts.

How else are you guys dealing with this issue?