Can ORF work behind a firewall?
Yes, ORF can work behind firewalls, but the Before Arrival filtering may be unusable in this scenario. Some firewalls behave like a proxy, first they receive the SMTP data and forward that to the server where ORF is running. Before email arrival, the email header is not available, so ORF identifies the sender server as the incoming SMTP connection remote peer. When ORF is running on the primary MX and receives emails directly from the Internet (or via a transparent firewall), this address above is the IP address of the sender server. When a proxy or proxy-like firewall forwards the SMTP data, the connection is coming from the proxy and so the address is the proxy’ss address. As many ORF tests use the sender IP address, these tests may not work and ORF’s performance may be lower. See Q: Before Arrival filtering does not seem to work, any ideas? regarding this.
