How to Zimbra Split DNS with dnsmasq

When you install Zimbra on a server behind NAT, your public IP is not configured in the server, instead, it gets routed to the server using NAT gateway. Zimbra wants the IP address of your MX record present in the server.

To solve this problem, we can use Split DNS. When you check the IP of the MX record from the server, it resolves to the internal IP address of the server. For everyone else, the MX record resolves to the public IP Address of the server.

IMPORTANT: Do not install Zimbra dnscache (unbound) as it listens on port 53, which will cause conflict with Split DNS.

Install dnsmasq

Install dnsmasq with command

Configure dnsmasq

Edit file

Add

Restart dnsmasq

Edit /etc/hosts file

Add

Edit /etc/resolv.conf

Add

Remove any other name server entry, do all DNS requests go to dnsmasq.

At this point, if you do a nslookup/dig for MX record, you should see your internal IP address.

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