Question about relay and costs

Julian Field MailScanner at
Sat Jul 9 14:01:01 IST 2005

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Max Kipness wrote:

>Hello ^Ö
>Hoping someone can offer advice on an issue I^Òm having.
>I have a server with the latest version of MailScanner, and DNS configured
>for the email domain with a cost of 10 pointing to this server.
>I have another server that is not running MailScanner (yet) in another
>location. It simply relays mail to the MailScanner server using Sendmail
>with a cost of 20.
>What's strange first off, is that tons of mail still passes through the
>server with cost of 20, even though the primary MailScanner server with
>cost of 10 never goes down. Anybody know how to prevent this?
The spammers don't follow the rules. In order to avoid your 
best-configured mail servers, they deliberately target the mail servers 
with the highest cost. So the genuine mail will be going to 10, and all 
the spam will go to 20. Your best bet is to even up the mail load going 
to each one. The best way to do that is to set them both to the same 
cost, use a virtual hostname (e.g. mx.your.domain) and have 2 A records 
for that hostname, which are the IP addresses of your mail servers. 
Also, you will need to change the IP address of your original 20 server, 
as it will have been hard-coded into a lot of spammers' target lists by now.

Take a look at the Wiki entry I wrote about this a while ago:

>The other question is what I might be able to do with the non-MailScanner
>server so that when the mail does get relayed back to the MailScanner
>server, it has the original IP of the sender, rather than the relay
>server's IP. I believe this is causing SpamAssassin not to tag email with
>SpamCop or XBL list scores.
You will have to do the MailScanner "Spam List" checks on the first 
server it hits. However, SpamAssassin checks all the IP addresses in the 
headers, so will provide far more useful results. You are using 
SpamAssassin, aren't you? :-)

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Julian Field
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