IP in headers and spam detection

[Julian Pilfold-Bagwell]

Hi List,

I have a question regarding running Postfix in a DMZ.  I have a UTM with 
a single IP address on it's red interface but our ISP provides a range 
of 15 IPs for hosting websites, mail, etc..

I have an external IP allocated and forwarded to the mail server, but 
when remote servers perform a reverse lookup, the header contain the red 
interface IP.  I tried setting proxy_interfaces = and smtp_bind_address 
= to the external IP but it still came out as the red interface.  Is 
there a way of pushing Postfix into using the external IP or do I have 
to mess with DNS.

Thanks,

Jools