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Help setting up E2K Mail Relay Security

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5 replies

by jedavidow

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I am at the end of my rope. My ISP is threatening action if I don't tighten up my SMTP security.

I run E2K behind a firewall to manage my email. Our Static IP is W.X.Y.Z, and we run a 192.168.0.X subnet. The E2K machine is 192.168.0.2, the router is 192.168.0.1.

I initially set it up like this:
-SMTP on port 25
-SMTP connector forwards all mail through my ISP's Smart host.
-Authentication: Anon and Basic
-Connection: All OK
-Relay: Everyone.

Of course, this was insecure. So I changed the Relay to include ONLY the subnet.

When I did this, ALL MAIL FROM THE INTERNET was bounced. The bounced mail included a line that said "Server cannot Relay for W.X.Y.Z".

So I included W.X.Y.Z in the resources that can Relay, and I had the same problem.

My server is acting like this: If I shut of Relaying abilities, it will not accept incoming mail from the internet.

Is that correct?

Why does this happen? What does Relaying have to do with accepting mail destined for my server?

I have heard of solutions that include 2 SMTP servers- one internal to Relay mail out and one to accept messages inbound. But again, if the inbound server has to have relaying available, how do I prevent it from Relaying for people outside my subnet?

HELP!

5 replies

by joseph moore

Go to the Open Relay Database for answers on how to lock down your mail server:
http://www.ordb.org/
You can also look up the IP for your mail server to see if it is listed as an open relay.

hope this helps

by jedavidow

I looked over there. The instructions for E2K presented by the MS articles were not helpful (they create the problem I stated above).

I would like to understand what is happening. Why can't I RECEIVE MAIL if I block relaying?

by nettek

Two things:
1. Under the Relay options, you should check "Only the list below", which you would leave blank unless you plan to allow a specific computer or domain to use your server as a relay, and then check "Allow all computers which successfullyauthenticate." This will not interfere with incoming mail, but will prevent relaying.
2. If you have an SMTP connector installed, make sure that under the Address tab that you do not have "Allow messages to be relayed to these domains" checked. This overrides all of your SMTP virtual server relay settings.

by jedavidow

The connector setting was the problem. Not sure how it was set. I found that info wading through sevral websites. But since you posted it first, you get the points.

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