We have a tri-homed ISA DMZ configuration. In the DMZ, that is using public IP addressing, we have a SMTP Relay server (W2K with SMTP service). We want this relay the receive Internet mail and then forward these mail to an internal E2K server that we publushed using a Secure Mail server publishing rule (configured for in-and outbound SMTP mail). We have enabled routing and configured a Custom IP Packet Filter for TCP port 25 for both directions. For incoming mail This works fine.
We ALSO want this SMTP relay server in the DMZ to receive all mail that comes from the Internal E2K server and is send to the Internet. The first part works great. Only the Relay server cannot communicate with an Internet host that we use for some reason. As I mentioned before, we have configured the IP packet filter for both directions, so that should work I guess.
The only thing I could think of is that the Server Publishing rule for the internal server is using port 25 and therfore the relay can only send mail on that port to the internal server and not to an external internet host. If this is the case, then my question is: how can you configure an SMTP relay server in a DMZ for internal AND external relaying????
As a test we have disabled the publish rule for the internal E2K server to see if this would give back port 25, but without results.
have you already looked into the IP packet filter log? You should have two packet filters: one for the inbound smtp traffic (local port = 25) and one for the outbound traffic (remote port = 25). Also, don't forget that the default gateway on the DMZ hosts should be the ISA DMZ interface. You can easily test the packet filters with the telnet command on port 25.
BTW --- I assume you have published the internal mailserver on the ISA DMZ interface only.
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All Forums >> [ISA Server 2000 Firewall] >> DMZ >> SMTP Relay in DMZ 
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