I have several "alias" email addresses that are forwarded to one primary address. How do I set that up?

If you have multiple email accounts within a domain which all go to one main account, you don't need to set up separate users with their own quarantines and spam filtering settings. You can simply add the secondary email addresses as aliases. An alias will inherit all of the spam handling rules (aggressiveness, whitelist and blacklist, quarantine, etc.) of the primary account.