I have this situation:
server 1 : ZMAIL.domain.com with 2 nics, one for Internet and one for LAN
server 2 : BMAIL.domain.local connected in LAN

The second server has the role to keep back-up emails for every account I made in server 1. I doubled all account from server 1 and I forwarded every account to its correspondent in server 2.

The problem is that emails are not delivered because DNS server (from ISP) does not know my domain.local (that's normal). Even after I set bmail.domain.local in etc/hosts with its private IP didn't solve anything because postfix checks mx record from DNS not from hosts.

I do have another local DNS in LAN (my domain controller 2008 R2) but Zimbra checks only its first DNS (from ISP).

Can somebody help me? How can I solve this?