I have an Edge MTA (Postfix) that I use to help reduce spam before it gets to my Zimbra server. Right now, it accepts all mail for my domain. However, if mail is sent to a nonexistent user on my domain, it still passes it through (as it should).
I'd like some thoughts on how to pass only messages to valid email recipients. I believe I can use the relay_recipient_maps parameter and create a list of actual users, but that requires manually updating them whenever I make any changes.
However, if I end up going this route, how should I harvest the email addresses so that I get a valid list which includes email addresses, normal aliases, domain aliases (email@example.com, firstname.lastname@example.org)?
What would be nice is to do lookups on Zimbra's LDAP for valid recipients (including regular aliases and domain aliases). Does anyone have any advice to offer in accomplishing this?