Spam issues while using Postfix as a two-way relay
- by BenGC
I want to use a Postfix box to do two things:
Relay mail from any host on the internet addressed to one of my domains to my Zimbra server
Relay mail from my Zimbra server to any address on the internet.
To try and accomplish this I have configured Postfix thusly:
mynetworks = 127.0.0.0/8, zimbra_ip/32
myorigin = zimbra_server
mydestination = localhost, zimbra_server
relay_domains = example.com example.org
transport_maps = hash:/etc/postfix/transport_map
local_transport = error:no mailboxes on this host
transport_map looks like this:
example.com smtp:[zimbra_server]
example.org smtp:[zimbra_server]
Now, this works and passes the Open Relay tests. However, I am seeing in the maillog that the server is relaying spam that has a From: address of <> to domains that are not mine. How do I stop this behavior?