You can create a catch-all email address that will funnel all non-specified address to wherever you want.
Go to Mail > Addresses in your webpanel and "create a new email address". In the top box, you can enter "catch-all" @yourdomain and it will catch all addresses not already set up. Dreamhost does advise against it because you could get a lot of spam.
I have this on several of my domains and if I start getting spam, I'll go back to panel and make all email to that address gets deleted automatically.