[ale] MX Records and Spam

[Fulton Green]

On Tue, Apr 20, 2004 at 09:56:07AM -0400, John Clark wrote:
> I am currently running a Red Hat 9 Server (Hosted with Server Beach) and
> I am trying to find out more information about MX Records.
> 
> I ran into a problem last week where I could not email my girlfriend.
> BellSouth would reject the email as:
> 
> Connected to 205.152.59.32 but sender was rejected.
> Remote host said: 550 The sender domain must have a valid MX record.

BellSouth turned the MX check on just within the previous twelve or so
days.  It bit both my personal email and a listserv that I manage.

> Okay... So I use Server Beach's tools to add an MX Record, and overnight
> my Spam triples. Yikes!

My theory is that one of those spam channels depends on finding an MX
record for a particular email's domain, and it won't waste the bandwidth
or processing time if not found.  Given your estimate of the spam traffic
increasing by 200%, I'd say that it's the Russian zombie network that all
of a sudden has discovered that the address in their database with your
domain finally has an MX record.

> I am a bit of a novice when it come to email (we run Qmail). Can some one
> explain to me what is going on in very small words, or perhaps point me
> at some relevant articles? Is there any way to fix it?

Alright, small words now.

The MX (mail exchanger) record for a particular domain contains the
address of the host that can be expected to receive incoming mail on
behalf of the domain.  For example, the MX record for the FultonGreen.com
domain points to a server on the Internet with the name
root.fultongreen.com.  This server happens to run the mail exchange
service responsible for taking in my incoming email (over half of which
is now spam, by the way).  If I ever got really dissatisfied with how
my hosting provider deals with spam, I could always have them reset the
MX address to a third-party server (on which I would have an account) that
would handle email better.

The takeaway: Sorry, but you'll need that MX record you just added.  And
until an Internet task force comes up with a better way to authenticate
the origin of an incoming email, you'll have to find a good filter for
your newfound spam traffic.