Postfix not delivering to Zimbra

[jbAZ]

Hello,
I am setting up Zimbra in the Split Domain scenario with an external "Master" MTA server (server3) - sendmail with existing pop/imap accounts - and Zimbra server (server4) running as a slave. They both will be handling mail for example.com.

To test mail forwarding from the main MTA (server3) to a zimbra account, i have a .forward in the home directory of username with server4.example.com correctly in the contents. Logs show that the mail is sent correctly to Zimbra/Postfix (server4). It looks like zimbra is refusing the connection to localhost from Postfix via LMTP?

/var/log/zimbra.log on server4:

Feb  8 19:40:04 server4 sm-msp-queue[22812]: l1898vNk008217: to=username@example.com, ctladdr=zimbra (1010/1011), delay=09:31:07, xdelay=00:00:00, mailer=relay, pri=2640060, relay=[127.0.0.1] [127.0.0.1], dsn=4.0.0, stat=Deferred: Connection refused by [127.0.0.1]

server4's config from admin console:
GENERAL:
Display name: server4.example.com
Description:
Service host name: server4.example.com
LMTP advertised name: server4.example.com
LMTP bind address: 127.0.0.1

When I just do a "mail" command from a normal shell for this username account on server4, I can see the mail. It just does not seem to be getting into Zimbra. Outbound Mail to server3 (the main MTA) works fine.

Also, do I need to have an actual UNIX account on the server for each user in Zimbra?

[phoenix]

You can't bind it to 127.0.0.1, Zimbra has to have an IP that has DNS A & MX records pointing to an IP address and not the loopback address. Unless I've misunderstood what you've done?

No, you don't need a unix account for each ZImbra user, the users are provisioned in Zimbra only.

[jbAZ]

Also - Why would I need an MX record for this server if it's not the MTA for the domain?