What are Secure Email Servers?
An email server is a computer system that handles the delivery of email over a network. With a significant percentage of cyberattacks originating in emails, it is critical that email servers are configured securely. The following are tips for ensuring that your email server is configured to offer your organization the most protection against cyberattacks:
SSL certificate. Secure Sockets Layer (SSL) certificates are standard security technology for establishing secure links between networked computers. SSL certificates can be used to encrypt email servers, as well as websites. You can secure your email server with an SSL certificate that encrypts emails in transit and authenticates the sender’s legitimacy, ensuring that third parties cannot read your emails.
S/MIME. Secure/Multipurpose Internet Mail Extensions (S/MIME) are email signing certificates that can sign emails in transit and in the inbox. All emails are signed individually ensuring that you will not be impersonated.
MTA-STS. A Mail Transfer Agent Strict Transport Security (MTS-STS) is a verification check of incoming emails that only permits emails to be received through secure authenticated servers, using TSL 1.2 or 1.3. MTA-STS helps to protect your contacts from receiving unauthenticated messages sent via insecure connections, such as those where someone could insert malicious software, modify data in transit, or carry out man-in-the-middle attacks.
DNSBL. Use Domain Name System Blacklist (DNSBL) to check and reject emails from IP addresses that are known to send spammy emails and/or malicious links.
Firewalls. Email server firewalls screen outbound and inbound email traffic based on rules set by your email server. Firewalls will alert you to unusual activity and can deny email traffic, based on the rules that have been set by you. Firewalls defend email servers against DDoS attacks, viruses, and spam.
DMARC. Domain-based Message Authentication, Reporting, and Conformance (DMARC) protocol verifies the authenticity of emails by using Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM) to assure users that email is coming from an legitimate source and that the email has not been tampered with. DMARC defends against email-based cyberattacks such as business email compromise, phishing, and spoofing.
rDNS. Reverse DNS lookup (rDNS) allows users to find the hostname of an IP address to see if email messages came from legitimate servers.
SSH. Secure shell (SSH) is a method of authentication involving the use of cryptographic keys to prove a digital identity is the legitimate and authorized user. This is done with a public key and a private key, allowing users to be authenticated without passwords.
Updates. Updating email server software and firmware to the current iteration with patches and updates will fix bug issues and address vulnerabilities, helping to prevent cyberattackers from gaining access to your email server.