Okay... got zmlocalconfig figured out... and I still get an error when trying to send to mailing lists (but not to users).
<ml@zimbra_host>: host zimbra_host[66.228.xxx.xxx] said: 550 <ml@hostname>: Recipient address rejected: zimbra_host (in reply to RCPT TO command)
Mailman has no problems sending out however.
Any ideas? I've tried looking around on Mailman's lists, but all of their problems/solutions are listed for old old versions (~2.0, installed 2.1.9).