I'm getting lots of spam to one of my domains, and rejected mail is going into my queue and not rejected at the SMTP session level...

Example:
One of my hosted domains is set up to reject email to unknown mailboxes through the cPanel settings. A spammer sends email to a non-existant address like info@domain.com from an email address that doesnt exist like v82na.27hs@spammer.com. During SMTP negotiation, the server accepts the non-existant info address (even though it's supposed to fail, according to the settings for that domain), and later generates a failed message that goes into my queue. But, since the spammer used a fake email address, it stays in my queue several days.

Is there any way to configure it to 5.5.0 the email at the SMTP level? My queue is full of rejected email (approximately 40MB) that has nowhere to go.