Question

Exim mail server on Fedora with WHM

Asked by: NetMatters

We have a mail server (85.118.232.134) as part of a WHM setup which is hosting many websites.

I have done a relay test on mailradar.com all of which fail but im not quite sure why.  Is anyone able to make some suggestions as to how i can make sure this server isnt being used for any form of open relaying?

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Asked On
2009-09-04 at 05:48:27ID24707509
Tags

Mail Relay

,

Exim

,

Linux

,

WHM

,

Cpanel

,

Fedora

Topic

Email Servers

Participating Experts
1
Points
500
Comments
6

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Answers

 

by: nociPosted on 2009-09-07 at 06:34:44ID: 25274960

Does the test fail (bad test) or is the test result for open relay 'fail' i.e. it isn't an open relay.

Here are other web based open relay testers:
http://www.abuse.net/relay.html
http://www.spamhelp.org/shopenrelay/

Tool to be used inhouse:
http://www.brandonhutchinson.com/Open_relay_test_with_mrt.html

 

by: NetMattersPosted on 2009-09-07 at 07:09:03ID: 25275170

Sorry for the lack of clarity.  When i did the Open Relay test on mail radar all 18 tests come back with [Test Not Passed] then at the bottom states: All tested completed! Relays accepted by remote host.

When i performed the test from www.spamhelp.org it states: Testing 85.118.232.134 on port 25... successful! - the SMTP server is NOT an open relay

The IP address has been blacklisted with blackscatter.org a couple of times.  and messages from our server often dont get a great spam score even if there is very little in the message ie: a subject line, and a message that states "this is a test message from (email address)".

 

by: nociPosted on 2009-09-07 at 07:49:31ID: 25275421

I can't access blackscatter.org (Non Existant) ; backscatter.org (parked for free). So it seems to be gone.

Backscatter spam is spam that is sent to you Appearing to be from mr X@y.Z,
so you notify X@Y.Z that you received spam from him.... (nice of you to warn, But)
if spammer mr S@mail.source sends you a mail appearing to come from X@y.Z and you notify X@y.z you are delivering the so call backscatter spam.

Maybe you can stop the service of sending notifications of non-delivery etc. that should prevent you mailserver being listed as a (backscatter) spam source.

When I get home i'll take the mailradar.com check myself. and see... but it's result seem quite inconclusive..  The problem might there may be false positives, where you have a frontend for receiving mail, and later on check for spam etc.  (amavisd etc setup)  in that case you might appear to be an open relay up front, but make up for it during the mail processing.  
The right evidence is that a mail sent through your mail server cannot endup in a spamcheckers honeypot, if it does then you're running an open relay.
 

 

by: NetMattersPosted on 2009-09-07 at 09:30:25ID: 25276085

I just double checked this as www.backscatterer.org - i need to get my eyes tested.

The spam checking is done by the mailserver itself with SpamAssassin - i don't know if this is of any use to you.

Do you have any idea how i can turn off the delivery errors globally.  I did recently find a setting in WHM to check and rejec messagest at SMTP time and turned that on.  So im guessing it will tell the sending mail server that the message delivery failed instead of sending a message to the supposed sender.. is that correct?

I really appreciate your help with this.

 

by: nociPosted on 2009-09-07 at 10:47:46ID: 25276412

If it is spam related it is in the spamassassin configuration: (this is from my amavisd config file).
%final_destiny_by_ccat = (
  CC_VIRUS,      D_DISCARD,
  CC_BANNED,     D_DISCARD,
  CC_UNCHECKED,  D_PASS,
  CC_SPAM,       D_DISCARD,
  CC_BADH,       D_PASS,
  CC_OVERSIZED,  D_BOUNCE,
  CC_CLEAN,      D_PASS,
  CC_CATCHALL,   D_PASS,
);
So it's handled in a wrapper around spamassassin with mine.
I only bounce oversized to warn the sender, the others are either discarded or passed on.

 

by: NetMattersPosted on 2009-09-21 at 01:35:16ID: 25381088

Many thanks for your help.  Part of it was an issue of messages being bounced - one of my colegues had set it to bounce messages with high spam scores which is why i think we were on backscatter.org.  We haven't been listed on here for a while now which is good.  I have checked that the rest are either discarded or allowed and seems to have improved things.

Still not sure why mailradar.com is still stating that we accept relays.

20120131-EE-VQP-002

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