Secure email gateways, or SEGs for short, are email security solutions that have been proven effective in detecting and blocking phishing emails. If your email infrastructure is the castle gate of a kingdom, then your secure email gateway is a group of guards equipped with special skills to ward off invaders and unwanted guests (here, malicious emails).
These security solutions sit in line on the path of emails from the public internet to the email server. Moreover, these days, SEGs are integrated with machine learning, making them all the more relevant, accurate, and inclusive of all email threats.
What is a secure email gateway?
A secure email gateway is a suite of email security tools that uses signature analysis and machine learning to spot, block, and mitigate potentially harmful emails before they make their way to recipients’ inboxes. This simply means that before an email enters or exits mailboxes linked to your email-sending domain, it needs to pass through a secure email gateway first. Then, it examines suspicious emails for red flags; if red flags are detected, the email doesn’t get delivered at all.
However, the solution is somewhat outmoded and fails to detect newer attack techniques, including social engineering.
How does a secure email gateway work?
A secure email gateway works by behaving as a proxy for your email server. It operates using either of the two methods-
DNS MX record
To route emails through a Secure Email Gateway, the MX records of the domain are configured to point to the SEG instead of directly to the organization’s mail server. This setup ensures that all incoming email traffic is directed to the SEG first.
API integration
APIs enable different software systems to communicate and exchange data seamlessly. In the context of a Secure Email Gateway, API integration involves connecting the SEG directly with email platforms (like Microsoft 365, Google Workspace, etc.) to monitor, analyze, and control email traffic.
Unlike the traditional method of routing all email traffic through an SEG via MX records, API integration allows the SEG to connect directly to the email platform’s API.
This direct connection enables the SEG to access and manage email data without altering the existing email flow.
Features of a secure email gateway
Cybersecurity experts emphasize using a secure email gateway because of its following set of features-
Content disarm and reconstruction
The content disarm and reconstruction feature deconstructs malicious files in an email, strips out the harmful content, and remakes a clean, non-harmful version that is sent to the recipient.
Sandboxing
It’s unsafe to analyze some suspicious email attachments in a normal environment, especially zero-day threats, as they could leave a larger impact on the overall technical infrastructure. So, such files are examined in a safe sandbox environment, where SEGs can run malicious codes without jeopardizing the organization’s privacy, operation capacity, and reputation.
Data Loss Prevention
People often exchange sensitive data via email. SEGs’ Data Loss Prevention solution identifies and protects intellectual property in emails by averting their insecure transmission.
Anti-phishing
These solutions, embedded in a secure email gateway, identify and block common phishing threats, including malware delivery, data exfiltration, and credential theft.
Post delivery protection
An SEG might miss some threats during its inline email inspection, particularly zero-day threats. Post-Delivery Protection utilizes API integrations with an email service to remove a malicious email from the user’s inbox. Because the user might have already opened the email, it also issues a security alert about a potential intrusion.
DMARC
DMARC, which stands for Domain-based Message Authentication, Reporting, and Conformance, is an email authentication protocol that prevents phishing and spoofing. It empowers domain owners to instruct the recipients’ servers on how to deal with emails sent from their domain illegitimately.
Limitations of a secure email gateway
There are two aspects where a secure email gateway falls short-
Perimeter focused protection
Many SEGs direct email traffic intended for the corporate email server through a cloud-based proxy for inspection before forwarding it to its final destination. While this approach protects against external threats, it fails to address internal threats.
Poor OPSEC
It’s important to change your DNS MX record to point to Proxy if you want to enable certain secure email gateways. Showing the solutions in use empowers threat actors to plan attacks to bypass defenses.
Please note while SEG is an effective solution, it can miss some email attacks. So, it’s suggested that you also ensure email authentication protocols like SPF, DKIM and DMARC are in place for your domain.
