Customers of CardinalFactor.Net often seek advice and support to address concerns about Unsolicited Commercial Email (UCE) otherwise known as SPAM, falsely identified SPAM, and how our mail server handles these annoying problems.
Our mail server runs a software program called "Postfix". Postfix is quickly becoming the mail server of choice among ISP's and corporations for its ease of configuration in preventing UCE in addition to integrating with another product called Spam Assassin. Combined, we are able to offer a two-pronged approach that reduces the amount of UCE arriving in a users mailbox.
Stage 1: Postfix
When an email arrives at our server Postfix tests for a number of things. For example, an email comes in for email@example.com and the email says it is from firstname.lastname@example.org. Our server will first verify if indeed the domain portion is valid '@somecorp.com': if this domain isn't registered then this email isn't legitimate, if it exists then its likely legitimate and is sent to stage 2.
Stage 2: Spamhaus
Further analysis includes using an externally managed checklist called "Spamhaus" (www.spamhaus.org). If an email makes it through these checks it is then passed over to Spam Assassin for content filtering. It is at this stage where the potential for false positives can occur -- the email is scanned for content such as "is it HTML", "does it contain the word Viagra", etc. Those content checks are subject to fallibility and can possibly lead to false positives. The potential for false positives is minimal because the stage one checks are where 95% of email is rejected. The remaining 5% of rejected email is done on content filtering.
Why does the first method accurately reject invalid email?
The first method of rejecting email is successful based on a simple fact: 95% of the SPAM email coming into a mail server is from 'forged' email addresses. An example of this is a spammer forges an email saying its from hotmail.com but when our server checks its really coming from cablemodem_user.verizon.com.
Why does the second method accurately reject invalid email?
The success of the second method for rejecting email is based on the tried and true methods spammers use to entice someone into clicking on a link and pulling a user into a website for some product or other. The product used at this stage is Spam Assassin (http://au.spamassassin.org/index.html). Spam Assassin is highly configurable and we set the tolerance level higher than the default. This allows a greater set of emails to not be marked as spam. However, after a one year trial period where tagged spam email was forwarded on to our users, the feedback was that these settings were indeed tagging spam as spam and not resulting in false positives. All our users requested at this point that we drop tagged spam and not send it to their inbox. However, this is a configurable option. If you so chose to have tagged spam email forwarded on then we can configure it that way for you.
CardinalFactor.Net and its methods of blocking UCE (spam) uses sound routines for checking if spam comes from invalid senders in the first place. Secondly CardinalFactor.Net uses the premier spam scanning engine for content checking. Finally CardinalFactor.Net uses McAfee anti-virus scanning to prevent viruses from reaching users inboxes.
For greater safety and security -- not to mention a vast reduction in the irritation that spam email represents -- we encourage our customers to take full advantage of server-side email filtration. These methods are becoming more sophisticated with each passing day. It requires only modest configuration on our part to set up your mailboxes and direct mail to our servers.
If you find that our service isn't meeting your needs or living up to our claims we can simply direct mail to you unfiltered. Even if you are operating a corporate mail server, you can still use our server as your Anti-Virus, Anti-Spam gateway. We do this for several customers and they have been quite pleased with the service.
We hope this bulletin was helpful. If you have further comments or questions, please fill out the inquiry box below and we will reply immediately.