MS Exchange Experts,
At my location we have 2 firms that share a domain controller and Exchange store, however each firm has a separate domain (i.e. domain1.com and domain2.com). We currently have an issue in which some of our outbound email gets caught in SPAM filters due to reverse DNS lookups not matching forward DNS lookups. Right now have 2 PTR records for the same public IP address. This triggers SPAM filters as the expectation is that each domain will have one PTR record. Our planned solution is to have MS Exchange 2003 relay mail on separate private IP addresses based on email address, then have a firewall rule that will forward local SMTP traffic out on separate public IPs based on the internal IP. For example, we have our MS Exchange Server (also the domain controller) set up with two private local IPs (let's say they are 192.168.1.251 and 192.168.1.253). If a user sends email from domain1.com it will go out on local IP 192.168.1.251 and if another user sends email from domain2.com it will go out on 192.168.1.253. On the firewall, we should be able to set up a rule that will take SMTP traffic from 251 and forward it on one of our public IPs and do the same for 253 on a different IP. Is this possible and if so, how would we set it up?
We will be implementing this with a Cisco ASA 5505 firewall and MS Exchange 2003 on Server 2003 Enterprise Edition