Anti-Spam email filtering services filter an organization’s inbound and outbound email traffic. Inbound email filtering scans messages addressed to users and classifies messages into different categories. These include, but are not limited to: spam, malware, adult, bulk, virus, impostor, suspicious links, and others. Outbound email filtering uses the same process of scanning messages from users before delivering any potentially harmful messages to other organizations. Organizations can deploy this functionality as a cloud service or as an on-premises appliance, depending on their requirements.
Email Filtering Techniques
The techniques used in email filtering will determine how effectively mail is routed. An organization should consider what they want in an email filtering solution. A combination of the following techniques can help organizations achieve maximum effectiveness:
- Reputation-Based Email Filters—Attempts to stop spam or allow legitimate email by filtering out known spammers or approving trusted senders based on reputation databases. Reputation Block Lists (RBLs) are lists of domains, URLs, and IP addresses that have been analyzed and deemed as possible security threats. RBLs are one of the main ways organizations can protect against spam.
- Whitelisting—Provides organizations the ability to determine which senders they accept email from by adding them to a list.
- Blacklisting—Provides organizations the ability to determine which senders they want to block email from by adding them to a list.
- Greylisting—Allows an organization to defend against spam by temporarily rejecting any email from a sender that it does not recognize. If the mail is legitimate, the sending server will try again after a delay, and the email will be accepted.
- Anti-virus—Protects against new and existing viruses and other forms of malicious code using signature-based and non-signature-based technology.
- Content Analysis—Offers the ability to block an email based on the content of the message. For example, if a message contains certain words, the content filter can determine that it is a spam message. Another example is if the message contained an attachment and the organization doesn’t want to let it through. Another form of content filtering is Bayesian analysis. Bayesian analysis filters spam by learning from each message it scans. The more messages are scanned, the greater the effectiveness of the analysis.
Organizations will have better protection from spam and other unwanted mail by having the above techniques included in an email filtering service.
Free Email Filter vs. Other Software Solutions
Organizations deciding what they need from an email filtering service need to understand what anti-spam techniques are offered. Not all email filtering services are created the same. Organizations have the option to go with either a free email filter or paid enterprise solutions. Email filters that can be used for free are typically cloud-based set-it-and-forget-it, with low overall management and time commitment. However, they may not provide all of the aforementioned techniques to provide the most effective email filtering. You need to understand exactly what is offered when deciding whether or not to go with a free email filter or an enterprise solution.
With an enterprise solution, you have the option to choose either an appliance-based or cloud-based solution. And you will typically find the vast majority of email filter techniques are included to protect your organization against spam and other unwanted emails. Another advantage that you get with an enterprise solution is the ability to create your own custom policies and rules specific to your organization. This gives you power over how your email is filtered.