All About Email Filtering Service: Types Of It & How It Works

Nobody likes to be bothered by unnecessary and irrelevant things when in the middle of something important. This becomes all the more troublesome and infuriating if such the distraction involves spammers and threats to your organization. Emails are one of the most widely used platforms by adversaries to make spam messages reach your inbox. Hence, it is of utmost importance to ensure that you have proper email security services that prevent such fake emails from reaching you when all you want to focus on is work!

There are thousands of email filtering services available today that aim to facilitate a spam-free working environment for you. Enterprises across the globe seek the help of some email gateway services or other email protection based products to protect themselves against malware better.


email gateway providers

Secure Email Gateways

The email gateway definition can be expressed as a service that enables you to make the emails received go through a virtual ‘gateway’ wherein they are scrutinized for the presence of any malware or other harmful content. This gateway ensures that only those emails with genuine and harmless content reach your inbox and discard the ones that appear dubious.

How Email Gateway Works

As mentioned, email gateway solutions protect from the attacks of adversaries that originate from emails. The gateway scans both incoming and outgoing emails for any malicious content and provides the following four security features. If you take a look below at how email gateways work, you can see how email filtering service is an integral part of the whole enterprise security solutions.


  • Blocking of Virus and Malware: One percent of all emails that crowd our inboxes are emails with viruses and malware. Hence the email gateway service comes with the provision of blocking these emails with viruses and malware content.
  • Spam Filtering: All email gateways give considerable focus to the deletion and handling of spam. Since spam is where all the malicious activities begin, they take special care to filter those emails for the safety of the user. Not only does spam filtering stop emails from unknown sources and spammers to reach the end-user, but it also detects standard techniques used by attackers to identify them better in the future.
  • Content Filtering: This provision lets a user filter their outgoing emails to ensure that no private attachments, images, or files are sent to outsiders even by mistake. This is like an added protective measure against data theft and further enhances your overall privacy and security.
  • Email Archiving: Email archiving is a feature that makes organizations hire different and specialized services altogether! It is essential in making your systems function smoothly, for reducing storage space and for efficient management and handling of critical data. However, email gateways these days come with this much sought after provision.
email gateway service
email gateway service provider

How Email Filtering Services Work

Typical email filtering services are of two types: list-based filters and content-based filters.

List-Based Filters

List-based email filtering works by using a preset list of senders marked as either spammer (blacklist), trusted senders (white list), or unconfirmed and treated as suspicious (greylist). The user or an organization’s system administrator can create these lists. Based on these categorizations, only the messages from trusted origins are allowed to enter your inbox.

Content-Based Filters

Unlike list-based filters that block or allow emails from a particular IP address or email ID, content-based filters scan and evaluate the email contents – words and phrases in the messages – to analyze their authenticity potential for threat. Content-based email filters are also called rule-based filters as they review the content of email messages according to preset rules and policies to decide whether may or may not contain a threat to the recipient.

The three main types of content-based filters are word-based filters, heuristic filters, and Bayesian filters.

For individuals or organizations with a tight budget, it may not be feasible to allow a budget for a premium email gateway service. However, you can find yourself an email gateway free of cost with a good bit of research and analysis. While there are many exceptional email gateway services available for a specific subscription fee, there also exist several other decent service providers whose services are free of cost.

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