Spam Filtering Companies

The Methodology we Employed for Choosing the Leading Email Spam Filter Providers

Spam filtering is just one part of the services that cyber security experts offer. But considering that 92% of the malware being delivered using email, choosing a dedicated provider can be a real game-changer for your business. In the following section, we outline each step of our evaluation methodology and detail the reasons behind our rankings.

Website Visit

Our evaluation methodology starts with a website visit. We thoroughly examine each company’s website to determine any client and/or industry focus and to get an initial overview of the services they offer. Moreover, we scout the portfolio and case studies to figure out their approach and problem-solving skills. This also keys us into their experience and expertise in dealing with spam emails. 

Types of Spam Filtering Solutions 

The next step involves a deeper exploration into the types of solutions the companies offer. This information doesn’t affect rankings but helps us classify the companies and provide you with useful resources for choosing the best one.

Appliance-Based (On-Premise) Filtering

Many businesses need on-premise solutions because of the high level of customization they offer. In this case, the filter is physically located in servers, sitting behind a network’s firewall, looking for email threats. The service provider takes care of the updates and provides technical support to guide businesses through any issues that might arise.

Cloud-Based Spam Filtering

Cloud-based filtering is a more cost-efficient software solution since it doesn’t require the purchase of a costly appliance like on-premise filtering does. This type of cloud filtering is also the simplest one to deploy—it can be installed on-demand, has low maintenance costs, and requires straightforward configuration. Although the software is in the cloud, the user gets total control over their filtering options. If you need help developing an actionable strategy, you can always seek help from the most reputed cloud consulting companies. 

Hosted Spam Filtering

A hosted filter is based within the cloud and can be active before any email gets to the network. As with most SaaS products, this hosted filtering service has minimal maintenance costs and is available on demand. Usually hosted spam filters are run by a third party, but the client still retains full control over their filtering policies. 

Open-Source Spam Filtering

Open-source anti-spam programs have great algorithms. They use robust frameworks and plugins to integrate a wide range of analytical tests on emails, making it hard for spammers to identify a target for their messages to work around. On top of that, users can easily configure every option. However, open-source spam filters usually require a large amount of manual tuning, which is a potential downside for users. Also, the costs for maintenance and infrastructure often exceed the license cost of a good filter. 

Spam Catch Rate vs. False-Positive Rate

When it comes to fighting spam, statistics matter. Thinking in terms of error rates, it’s important to know how successful a specific company is with its email spam filtering services. To assess this, we look into the spam catch and false-positive rates. 

The catch rate indicates the percentage of all email messages that have been identified as spam. And the false-positive rate expresses the percentage of legitimate emails that are falsely flagged as spam. 

When we compare these two values, the first needs to be above 99% and the latter below 0.05% for a company to get a nice spot in our table.

Spam Filtering Techniques

Different methods apply to different types of filtering solutions. Companies should use several methods to increase their anti-spam success rates. No technique is 100% bulletproof, so combining several of them gives better results in this regard; consequently, this kind of strategic approach will boost a company’s rank in our table.

Blacklist

Blacklist is one of the most popular filtering methods. It attempts to stop unwanted emails by blocking a specific address that’s been previously used to send spam. When a message is received, the spam filter will check it and determine if its email address or IP is on the blacklist. If it is, the message will automatically be delivered to the spam folder instead of to the inbox. 

The potential downside with this technique is that sometimes blacklists can confuse legitimate senders with spammers. This usually happens if the legitimate sender and spammer use the same IP address or if the scammer switches the IP address to cover their tracks. 

Whitelist

A whitelist is one of the most-used spam filtering solutions. It uses a system opposite that of a blacklist to block spam. Instead, it enables you to choose which senders to place on a trusted-users list, meaning you agree to receive mail from them. Most spam filters combine a whitelist with another methodology to reduce the number of legit senders assigned as spam. Still, it’s not best to use a filter that only uses a whitelist method because then anyone who wasn’t approved would be blocked.

Graylist

Many spam filtering companies offer graylist—a filtering technique that protects email from spammers who tend to send batches of junk mail. A receiving server with graylist enabled will reject messages from unknown users while sending a failure message to the originating server. Usually, legit servers will attempt to send the message again, which would indicate that the message can proceed to the recipient’s inbox. Graylist’s possible disadvantage is delayed mail delivery, which makes this technique a bit inconvenient if you’re expecting time-sensitive messages. 

Content-Based Filters

A content-based email spam filter assesses the words and phrases in the messages, through which they determine if the email is spam. One of the main limitations of this method is that its recommendations are based on interests specific to the user. 

Word-Based Filters

A word-based spam filter blocks emails that contain specific words. This is a pretty useful method since many emails contain words that aren’t usually found in legit messages. However, if it’s set up to filter messages containing commonly used words, it can create false positives. 

Real-Time Blackhole Lists

This method is very similar to the blacklist technique but with less hands-on maintenance. Most real-time blackhole lists are maintained by third parties who create blacklists for their users. When an email comes in, the filter is linked with the third-party system in order to determine whether the sender’s IP address is on the list. This method is time-efficient but, at the same time, likely to generate the false positives that happen when a spammer uses a legit IP address to send junk mail.

Bayesian Filters

Bayesian is undoubtedly the best enterprise spam filter. It uses the laws of mathematical probability to determine which emails are spam. In order for this filtering type to work perfectly, the user needs to first flag each spam message manually. The filter will eventually pick out the words and phrases found in the spam messages and add them to a separate list. It does the same with the words and phrases found in legitimate messages.

Essentially, the Bayesian filter scans email content and compares it against these lists to calculate the probability that this message is junk. This method is extremely useful, and the longer it’s used, the more effective it becomes. The potential downside might be the training period required before it starts showing results. 

Heuristic Filters

Heuristic filters work in a similar way as any word-based spam filter. The difference is that heuristic ones block emails based on multiple terms found in the text rather than blocking the ones that contain a suspicious word. 

These filters scan email content and credit the words that are common for spam messages with higher points, while the words usually found in legitimate emails get lower points. All the points add up to make a total score, and if it’s higher than the limit set by the anti-spam app’s admin, the email is identified as spam and blocked. Heuristic filters are fast and effective but also tend to create false positives if a legit sender uses a certain combination of words in the email. Similarly, spammers can easily learn what terms to avoid and mislead the heuristic filter.  

The Challenge-Response System

Many spam filtering service providers offer the challenge-response system. This filtering type blocks emails by demanding the sender to complete a task before their message can be delivered. Essentially, the sender receives an email asking them to visit a specific page and enter the code found there into a special form. The email is delivered only if the task is completed successfully.

The challenges can all be resolved by a human, and since spammers usually use automated programs, they won’t be able to complete it. However, some senders might misunderstand the challenge or won’t take the time and complete it. Finally, if both the sender and the recipient use this type of filtering system, the apps will challenge each other in an infinite loop. 

Zero-Hour Spam Protection and Detection

Zero-hour threats via low-volume attacks are designed to remain undetected. This spam filtering method detects messages with spam, phish, or any malware that has already been delivered to the user’s inbox. The malicious content is then rendered harmless.

Quarantining

Quarantining temporarily stores the emails suspected to be spam. These messages are then reviewed and released from the quarantine (if they’re legitimate) or automatically deleted (if they are indeed spam) after a set period of time. 

Outbound Email Scanning

Malware infections can enable cybercriminals to gain access to accounts and use them to send spam. If this happens, it can hurt your reputation and blacklist your domain. This is where outbound email scanning comes in—it prevents a mistakenly blacklisted IP address. 

Spam Filtering Service Reviews and Testimonials

All of the above aspects of our evaluation methodology give us information as to what the core specialties of each company are, as well as the level of their expertise. However, learning how reputable each company is in the eyes of its clients is just as important. 

Therefore, we scout the customer testimonials found on the companies’ sites. Then, we dig a bit deeper and analyze the customer satisfaction rate by going through reviews on third-party sites. This usually presents the clearest picture. Along with taking note of all the good things about the company in question, we pay attention to the bad reviews. Still, unless the negative reviews are prevalent, we keep the company in mind and continue the evaluation. 

Pricing and Value for Money

Besides considering the enterprise spam filter reviews and ratings on the web, we make sure that the companies’ pricing policies align with industry standards and that there are no extremes in either direction. The option of a free trial is another important feature. Companies that provide it get a boost in the rankings. Finally, for classification purposes only, we determine what billing method the company uses—you may be charged per user or required to make a one-time payment, or maybe the company will leave it up to you to choose your preferred method. 

What to Consider Before Deciding on a Spam Filtering Service 

Before making a decision, make sure to consider the aspects outlined below:

Industry Experience

One of the most important things to consider when choosing an anti-spam service is whether the company in question has experience working with businesses similar to yours in terms of size and industry. Some of the companies on our list have a specific industry focus, which might be helpful when narrowing down potential candidates.

Management, Integration, and Ease of Use

The solution you choose needs to be easy to use and manage and have great integration features. You need to be able to handle the spam filtering options the company provides. Additionally, integration features are important because they increase your company’s overall efficiency. And having access to different tools like Dropbox or Asana will enhance the potential for a streamlined workflow.  

Flexibility and Scalability

The filter should be two things: flexible and scalable. You should choose the solution that enables you to add and remove users whenever you want and has no scalability issues if your business increases or decreases in size. The best cloud spam filtering service will offer subscriptions based on a specific number of users, and they’ll offer to refund the underused service subscription if necessary.

Support Communication Options and Availability

Many of the providers listed here offer 24/7 support. This is a great option because you’ll have a technologically savvy agent around the clock to handle any questions or issues that might arise at any time. So be sure to talk with your potential spam filtering service provider about communication options and availability. It’s best that you’re appointed a contact person who’s available to communicate through the channels that work best for you. 

Define Your Resources

Last but not least, determine your budget. Defining the resources you want to spend on email protection and comparing them against the rates that companies offer will help you finalize your list and quickly find your ideal partner.

Up to You

Protecting your business from unwanted emails that pose a serious security threat is easy with the right spam filtering service. We’ve provided you with a complete list of the best candidates, so all you need to do is follow our comprehensive guide and find your perfect match.