What Are Email Security Gateways And How Effective Are They?

Email security gateways or secure email gateways (SEGs) are a type of email server that protects organizations' or users' internal email servers.
Tom King
February 15, 2023

Organizations today are facing adversaries daily who are innovative, tenacious, and utterly relentless.

As soon as security professionals put controls in place to push back against cyberthreats—including phishing attacks, denial of service attacks, ransomware, and many more—hackers begin devising new threats and planning targeted attacks to get around those controls. Implementing a good email security gateway with strong security features is an excellent step to take towards enhancing organization-wide safety and keeping hackers away from your sensitive information and important data.

Email gateway protection helps to block malware, phishing attacks, spam emails, and a host of other unwanted email-borne threats from reaching recipients and compromising their devices, user credentials, email systems, or sensitive data. When so many of the threats organizations are currently facing are email-based, a security gateway can help to protect employees and sharply decrease the volume of successful attacks.

Secure Email Gateway Software Overview

Email security gateways or secure email gateways (SEGs) are a type of email server that protects organizations' email environment. As the name suggests, the server acts like a gateway through which all inbound emails and outbound emails must pass and be subject to scanning. These email security solutions are designed to block pre-delivery email-based threats before they can reach email servers, whether they be on-premises or cloud email clients, such as Microsoft Office 365 or G-Suite.

These solutions work to prevent the transmission of emails that break company policy, malicious emails that contain malware, or emails that transfer information with malicious intent. To achieve this, most secure email gateway features will include anti-virus and malware blocking, threat detection, spam filtering, phishing protection, content filtering, and email archiving.

Most enterprises use secure email gateways to protect themselves against prevalent email threats, including the highly common threat of phishing attacks.

How Do Secure Email Gateways Work?

A secure email gateway scans all internal, inbound, and outbound email correspondence for malicious URLs, malicious attachments, or malicious content. These capabilities provide protection against social engineering attacks like phishing and business email compromise (BEC) by quarantining or rejecting any emails that contain suspicious content before they can reach the intended recipients, with some systems allowing admins to access emails that have been quarantined if necessary.  

A secure email gateway also provides protection against data loss by scanning as outgoing email passes through the email server, with many solutions offering email archiving functionality to safely store emails for legal compliance and data management purposes. They often also come with continuity features that allow businesses to continue to access their emails even if their email network goes down.  

Additionally, secure email gateways come with a management dashboard that allows businesses to oversee a range of reports and analytics, offering enhanced visibility into all network email traffic and providing insights into business productivity and overall network security.  

Cloud Vs. On-Premises

It is up to each organization to decide if they want to deploy their secure email gateway solution on-premises—using either an appliance or virtual appliance—or as a cloud-hosted service. Choosing between these options will be influenced by whether the organization is currently using a cloud-based email service like Microsoft Office 365 or an on-premises email service like Microsoft Exchange. The decision depends also on whether the organization is interested in migrating services to the cloud, as well as their level of comfort with the idea of allowing data and services to exist outside the boundary of their own network.

When thinking about deploying on-premises appliances or software to protect email, it's important to consider your responsibility for the purchase, maintenance, and continual updating of the necessary hardware. Those choosing to deploy a secure email gateway as a cloud service need not worry about these responsibilities, as it is the security vendors' job to maintain service availability. Scalability is another factor to consider, especially for growing organizations and SMBs; a cloud-based service is equipped to deal with spikes and steady increases in both email traffic and the number of users, and so can scale to maintain performance.

How Effective Are Secure Email Gateways At Stopping Phishing?

A secure email gateway is often the first line of defense against common social engineering attacks, which makes sense when we consider that 96% of phishing attacks arrive by email.  

According to Cisco, over 86% of organizations have experienced at least one person clicking on a phishing link, which is particularly concerning when phishing also ranks as the second most expensive cause of data breaches, averaging a cost of $4.65 million according to IBM.  

A secure email gateway offers a layer of protection against phishing attacks by checking the domain of incoming emails, as well as scanning emails for suspicious content and flagging that suspicious content before it can enter the network.  

Effective security requires more than one preventative measure, and we achieve the most positive outcomes when we combine methods to form a more well-rounded security strategy. A well-trained workforce will get you so far, but to manually accurately detect and respond to phishing emails can be a complex, time-consuming, and error-prone process, even with the very best training and the most motivated workers. Implementing solid, comprehensive security awareness training alongside the right security tools provides organizations with a much more robust, layered defense.

To eliminate phishing threats effectively, you will need the right email protection security tools deployed across your environments. A secure emails gateway decreases the likelihood of successful phishing attempts by blocking the sender or segregating malicious messages into the spam section.

Benefits Of Email Gateway Services

Businesses choosing to utilize a secure email gateway can enjoy a range of benefits. There are obvious security benefits, as a secure email gateway will support employees by protecting them from common email threats like phishing attacks, viruses, and spam. This is a huge benefit for any organization as people are the most sought-after target for cybercriminals, with email being one of the most common methods attackers used to reach them. With a secure email gateway in place, security is improved, as is the experience of employees who can get on with their work feeling reassured that security does not begin and end with their ability to spot malicious emails. That they have support in place to help keep them safe from inbound malware and other email security threats.

Meeting business compliance needs are another benefit to consider. Many email gateways provide email archiving and encryption capabilities, meaning businesses can both improve their overall security and meet their compliance needs by securing their sensitive data and storing copies of emails for legal reasons.

A secure email gateway also provides business continuity; if the email client used by an organization were to go down, all email operations can continue to work as normal. This is because the email gateway provider will enable user access to a cloud-based email service if an email client, like Microsoft Office 365, were to become unavailable.

How To Ensure Your Secure Email Gateway Is Effective?

-       Take a multilayered approach to security

-       Ensure your provider has a lot of experience in security email gateways

-       Make sure whoever is providing the solution is also going to be doing the installation, giving you a managed deployment with competent customer support

-       Make sure the solution is not just installed, but also that your environments are fully locked down to only receive from the secure email gateway, with strong response capabilities

-       Make sure the partner deploying the email gateway has the technical expertise to do so without disruption or loss of email flow.


Email threats such as malware, viruses and spam can be highly damaging, both immediately and in the long term, but there are steps you can take to proactively boost overall security. Implementing a strong email security solution is a great place to start and can go a long way in making protecting your users and organization as a whole against malicious content distributed via email. A good secure email gateway solution, ideally one that uses machine learning, sandboxing, and predictive analytics, can provide you with real-time protection against today's cyber threats.

Constant Edge manages tens of thousands of email security users across hundreds of clients. All of our engineers are dedicated email security engineers, offering comprehensive email support from 4 am to 6 pm Monday to Friday, North American Eastern time.

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