Undeliverable Report - Blacklisting 1

[Borvik]

Okay here is our setup.

All mail enters through our Postfix server which does some basic header checks (reject zip files) and then forwards mail for our domain to our exchange server, and for other domains we host to a different mail server. So there is a total of 3 mail servers.

Here is where our problem lies. We get hit with a TON of spam. The first server (entry server) accepts it because it is going to a valid domain, but the 2nd tier server reject the forward because the users don't exist. The first server then generates an Undeliverable report and attempts to send that back to the original sender. The sheer volume of which is causing us to get put on blacklists.

Is there any way to stop that first postfix server from generating and sending those Undeliverable reports?

Thanks.

 

[Borvik]

Ok - I've made some progress, but I still haven't solved the issue.

The first server (the one in question) forwards the mail to the other two servers using: transport_maps = hash:/etc/postfix/transport.

I need to make this server aware of all the email addresses it can accept mail for - not just the domains - before it forwards it on to the correct server.

I've just completed a perl script (with some help from google) and connected the server to the domain, so that perl script can grab all the email addresses in Active Directory (could be used in a postfix config file - then have postmap run on it in in cron job - can be reformatted to fit the file it's going into).

How can I get postfix to reject unauthorized recipients for those domains it forwards to?

 

[zbnet]

You need to populate the relay_recipients table in Postfix.

http://postfix.state-of-mind.de/patrick.koetter/mailrelay/

is a good explanation.

 

[Borvik]

Thanks zbnet!

It has taken me several days to implement your suggestion, but I think I have it.

Now I just need to setup a cron job to auto-populate the relay_recipients, relay_domains, and transport files (and postmap them). Once done with that, I should be golden.

Thanks again.