The Best Spam Filter for Business – Key Factors to Consider

• Uptime guarantee: What is the uptime guarantee for availability of the spam filtering service? There is no point in having a spam filter with a very high detection rate that only works half the time! The best spam filter for business should guarantee over 99.9% availability of the spam filtering service.

• Ease of deployment: How easy is it going to be to deploy the spam filter in your environment?

• Ease of use and management: An email filter that is too complex is likely to be less effective at detecting spam and other email-borne threats. Its settings may be applied too high resulting in a high number of false positives or too low, thus reducing the effectiveness of detecting email threats.

• What is the spam detection rate? When selecting an email filtering solution, a key feature is the percentage of spam and emails containing threats that the solution can block at its optimal settings. Although most standard email hosting platforms offer a certain degree of protection against spam, they do not provide adequate protection against the increasing sophistication of cyberattackers. A higher percentage of unwanted or unsafe emails still evade detection. It only takes one click on a malicious URL or attachment for an entire network to be compromised.

The best email filter for business will use various techniques and tools to aid in the detection of email spam and other advanced email-borne threats.

• What is the average percentage rate of false positives, i.e., how many genuine emails are accidentally blocked or quarantined? The best spam filter for business should have a very low false-positive rate. You don’t want to have a whole bunch of important missing emails! Having to search for them every other time will be a time-consuming exercise and may cause you to lose potential business.

• Advanced threat protection: Beyond protection from unsolicited (junk) mail and viruses/worms/malware, does it protect against sophisticated attacks such as phishing, ransomware, business email compromise (BEC)/ CEO fraud attacks?

• Cost-effective: How much will the best spam filter for your business cost? Cost-effective is relative and the determination of what is cost-effective will vary from region to region. What is cost-effective in the US/UK may not be considered expensive in other countries - for instance, in Africa, Latin America, or Asia.

The best spam filters for business tend to start from approximately US$1 per user per month, but may also cost several dollars per user, depending on the solution and add-ons you choose (Some companies charge extra for support, for instance).

You can often get discounts for a large number of users or for contracts running for multiple years. In determining whether the best spam filter for your business is cost-effective, you also need to consider how much it will cost you to maintain your spam filter in the long run. Cost considerations should not just include subscription costs but costs that may be related to monitoring, maintaining and updating your solution.

• Does the solution filter outbound email? The best spam filtering service provider should provide outbound mail filtering – and preferably by default. If it doesn’t provide by default, don’t forget to factor in the cost of outbound email filtering when determining the cost of the email filter you plan to get.

• Scalability: How easy is it to scale? As your company grows, will it be easy to have new users’ emails filtered? A good spam filter will make the addition or removal of users easy and cost-effective. It will not require purchase of new infrastructure regularly. Subscription-based options that are per user or per group of users are an easier model to scale.

• Compatibility: The best spam filter for business will be compatible with a wide range of operating systems and email platforms. Choosing a compatible spam filter is important to give you flexibility to change your email platform or operating systems in future without having to go back to the drawing board in search for another spam filtering service.

• Free trial: The best spam filter will also allow you an opportunity to test its effectiveness in your environment for free, no obligations asked, for a reasonable period of time.

1. Outbound email scanning

Outbound mail scanning checks outgoing emails for malware and for content that could be mistakenly identified as spam. Some spam filters can be over-zealous and block mail for a misspelled title or too many spam-related keywords in the body of the email.

Malware could be present in outgoing email if, for instance, an employee had created a document on their malware-infested home computer and attached it to a company email.

If one of your organization’s outgoing emails is flagged as being spam or having malware, your organization’s IP address may be added to a real-time block list (RBL). An RBL is a global blacklist of known spammers and their IP addresses against which every spam filter compares every incoming email. To have your emails blocked globally would affect the flow of communication between your business and your customers and potentially damage your credibility.

When phishing attacks happen and mailboxes are compromised, they are often used to send further phishing emails internally and externally. Outbound mail scanning allows the security team to identify compromised email accounts and quickly mitigate the threat.

2. Greylisting

Whereas the real-time blocklists (RBLs) contain known spammers’ IP addresses, greylisting identifies spam from previously unknown sources. Greylisting does this by rejecting emails from IPs it does not recognize and requesting that the originating server resends them. Ordinarily, the originating server will respond to the request within a few minutes. However, a server sending spam emails will be too busy to respond, and the request effectively denied.

Greylisting is an essential feature of the best email filtering service for business because it eliminates spam from sources not included on real-time block lists and increases the spam detection rate from around 97% to close to 100%. It removes the 2% – 3% of unwanted or unsafe emails that evade detection and keeps your inboxes virtually free from all types of spam. NB: not all premium spam filtering services include this feature.

3. Phishing Protection and Malicious URL Blocking

Phishing protection and malicious URL blocking are two features of email filtering that prevent the delivery of emails containing links to unsafe websites. These crucial features of the best email filtering service for business help prevent scenarios in which employees disclose their login credentials to cyberattackers or visit websites that automatically begin downloading malware onto their devices.

Phishing is one of the most dangerous online security threats in the world today. A cyberattacker with an employee’s login credentials can use that information to steal, delete or corrupt data. For an organization in a highly-regulated industry, the breach of security could result in hefty fines and civil action for the failure to implement adequate precautions against data theft or unauthorized exposure. Again, not all premium spam filtering services include this feature.

4. Sandboxing

Although antivirus/antimalware engines are used to detect known virus and malware threats, new virus and malware variants are constantly being released. While these zero-day threats are added to definition lists when the threats are identified, there is usually a lag. Sandboxing plugs the gap by protecting against zero-day attacks. When a suspicious email attachment is received that is not flagged as malicious by the antivirus or antimalware engine, it is sent to the sandbox for further analysis to identify malicious actions.