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Stopping Spam in its tracks

by Tim Attwood on October 26, 2006

We’ve become so accustomed to spam cluttering up our mailboxes, that it’s hard to remember that there was ever a time without it. In fact, the origins of spam go back so far that it is unlikely that any of us were fortunate enough to ever enjoy a spam-free mailbox.

We can draw a lot of similarities between postal mail and email. However unsolicited postal mail and unsolicited email have some significant differences. With unsolicited postal mail, the cost of delivery is entirely covered by the sender. This is not the case with spam email. Of course the spammers will pay for part of the delivery cost, but the majority of the delivery cost is paid by the recipients’ email service provider in bandwidth, CPU usage and storage space. These costs are often passed on to you, the end user via your subscription fees. So spam is not only annoying, but it is costly to all of us. By some estimates, spam accounts for up to 85% of all email.

Here at SoftCom, in order to try and reduce these costs, we use a number of different mechanisms to try and eliminate spam – even before it is delivered to our email servers.  Currently, we use two important checks before accepting the email from the sending server.

  1. We check against a number of reputable RBL lists, or Realtime Blackhole Lists. An RBL is basically a list of email servers or service providers whose customers are responsible for the SPAM or whose servers have been hijacked for SPAM relay. Any connections to our email server from a server on the lists we use will be rejected, and the email will not be accepted for delivery.
  2. The second line of defense is to check the recipient email address against our list of users. Any email sent to a nonexistent user is rejected. This type of email can even be a result of an email dictionary attack, a technique often used by spammers to try and discover new email addresses to target with spam.

Surprisingly, these two types of connections to our mail server account for up to 92% of all attempted connections to our email servers. If we were to accept all of these connections that our email server capacity would need to be increased by as much as ten times just to be able to handle the volume. For a customer on our Basic linux hosting plan ($9.95/month), this could mean a price increase of up to $10, doubling the monthly fee. (But don’t worry, we don’t have plans to do anything as drastic as that!)

The remaining 8% of email that is accepted is then scored against our Anti-Spam system which uses a series of rules and checks to determine the likelihood that any given email is spam. Anti-Spam rules will result in an email being given points towards an overall score. In general, email with a score of 5 or greater is considered to be spam. About 42% of all accepted email scores a 5 or greater, and 58% scores under 5. This means that up to 95.4% of all email either attempted or accepted to email servers is spam or suspected spam.

In addition to all this, we perform Anti-Virus scans on all incoming email, as well as some Anti-Spam and Anti-Virus scans on outgoing email to ensure that our servers are a source of clean email.

But that isn’t all… there are some further steps you can take. Due to the way the Anti-Spam system works, you can choose from multiple options on how to handle the spam that arrives makes it to your inbox. You can choose to tag email scoring 5 or higher with SPAM in the subject, thus allowing you to create an email rule to sort or delete unwanted spam. You can choose to take no action at all. Or you could even make a custom rule which checks the email header for the Spam score, and filters your mail based on your own thresholds. This allows you to increase or decrease the sensitivity of the Anti-Spam setting on your own. For our Exchange customers, this can even be adjusted from the control panel.

And for those users who want to bypass the RBL checks, it is now possible for customers to whitelist servers that don’t pass our RBL checks, on a per account basis.  And we’re planning to provide this feature for Exchange customers in the near future as well.

Although we do as much as possible to keep your inbox free of spam, nothing is perfect. Spammers are always trying new techniques to get past our filtering methods. And since the volume of email requires the use of an automated system, there are from time to time both false-positives and false-negatives. But we aren’t letting our guard down yet and we’ll continue to do whatever we can to keep your inbox Spam free.


Tim Attwood
Product Manager
SoftCom Technology Consulting Inc.

Related posts:

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  2. Semi-Automated Whitelisting
  3. Seeking Redemption through Auto-Renewal
  4. Common Issues with FrontPage Server Extensions


Rodolfo December 8, 2006 at 10:15 PM

WordPress Trackback Spam!!!
I have installed plugins that prevent comment spams, but this won't prevent trackback to be blocked. I've been spam by many
MFA websites that most probably is from the same network with trackback, but they are not linking me on their website. May I
know how do they do it and how do I stop it? Without disabling trackback?
Thanks, and I'm using WordPress.

Tim Attwood December 12, 2006 at 10:47 AM

I’d recommend looking for help on the Wordpress Support forums. They’re very helpful… if you can’t already find the answer there, someone in the community is sure to offer some suggestions.

Stoddard February 4, 2011 at 9:38 AM

The Wordpress support forums are very helpful. I’m glad I checked them out.

Randy5 August 9, 2011 at 11:24 AM

Keep up the good work; I feel as safe from spam as possible.

Texas2Step August 15, 2011 at 8:04 AM

Now that I think about it, you’re right: I got spam way back when I got my very first email account.

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