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If youre like most businesses, its your main communication channel with customers. Here are some email server security best practices you can use right away to help create a secure email server for your organization

Imagine youre preparing for a hurricane thats coming your way (we Floridians are well acquainted with this procedure). You install straps to help make your roof more secure. You pull all your lawn equipment, furniture, and other outside items into your garage or shed. You board your windows and doors and buy lots of food and water in case youre stranded without power. But if you choose to leave your homes exterior doors open as the storm moves in, you can kiss your house and everything in it goodbye. Similarly, this is kind of what its like when companies dont bother implementing a secure email server.

Radicati estimates the total number of business and consumer emails sent and received per day will surpass 376 billion by the end of 2025. If you send emails but dont have a secure email server, then it means that any data transmitted through them is at risk of compromise. (Data is the lifeblood of your business you cant risk your sensitive info falling into the wrong hands.)

But what does it mean to have a secure email server? Lets cover 10 email server security best practices and remind you why implementing these measures is necessary to protect your business and customers.

Lets hash it out.

Much like the word secure implies, having a secure email server means that youre protecting your email domain and data from unauthorized usage. This means:

But how can you achieve these outcomes? Lets dive right into what you came to learn

The following email server security best practices list isnt a complete or comprehensive guide. However, this list provides you with a great starting place to help make your email server more secure.

A big mistake that organizations make is not taking the time to change their servers default settings and configurations. This may be because theyre in a rush or, perhaps, they dont realize just how risky it is to use the default settings. Regardless of the reason, be sure to take the extra step and change these settings.

This includes changing default login information as well. Account and password security are paramount in cybersecurity as a whole. If you use a default username and weak password combo to secure anything, its the equivalent of having the option of using a double deadbolt lock on your front door but opting to use a flimsy chain lock instead. Sure, it provides minimal security, but an attacker only needs to use a little brute force (get it?) to bust their way in and gain access to your home.

Using the default credentials (username and password) that comes with your server or software is like this. Its not secure and leaves your email server and its data at risk of theft and other compromises.

A mail transfer agent strict transport security is a verification check of incoming emails. According to Google, SMTP connections for email are more secure whenthe sending server supports MTA-STS and the receiving server has an MTA-STS policy in enforced mode.

Uh, sure. Great. But what does this mean? Basically, this is saying in laymans terms that if you have MTS-STS enabled on your organizations email server, itll only permit emails to be received via secure, authenticated connections (using TLS 1.2 or 1.3).

This helps protect your recipients against receiving unauthenticated messages sent via insecure connections (i.e., connections where someone could insert malware or modify data in transit, or whats known as a man-in-the-middle [MitM] attack).

If the senders digital identity cant be authenticated or they didnt have SSL/TLS enabled, then the message gets rejected.

Setting up a secure MTA is only part of the equation; you also need to take a few extra steps to help make your server and the inbound and outbound communications to/from it more secure.

Did you know that SSL/TLS also applies to email? Thats right, you can use SSL/TLS security to secure the communication channel of your messages. This allows you to encrypt the communications that transpire between your email server and other email servers that it communicates with. This way, no one can intercept the communications in transit.

Every time one of your employees sends or receives an email from someone, it creates a connection with that individuals email server. If that connection isnt secure, it means that anyone with the know-how can intercept that message in transit and steal or modify the data without the two original parties knowing what happened.

Of course, if youre using an email signing certificate to encrypt your email data directly (more on that later), then this serves as an additional layer of security for your communications.

Traditionally, IMAP or POP3 are protocols that are used for incoming emails (i.e., messages email clients grab from your mail server). SMTP, on the other hand, is used for outgoing emails. Be sure to set your services below to the following secure TCP/IP ports for incoming out outgoing messages:

Cybercriminals love playing dress up with companies brands and capitalizing on their reputations. Its not uncommon for bad guys to impersonate organizations as a way to carry out phishing scams. Check Point reports that the most impersonated brand of Q1 2022 was LinkedIn, which was involved in more than half (52%) of all phishing attacks they analyzed globally. In Q4 2021, Check Point said that DHL held that title, and Microsoft prior to that was the reigning champion of the title that no company wants.

Domain-based message authentication, reporting and conformance (DMARC) is an email protocol that helps to protect your domain against inauthentic usage by unauthorized individuals. The Internet Engineering Task Force (IETF) brought it into the fold as a way to help organizations protect their domains against these fraudulent usages. DMARC builds upon two other authentication protocols to ensure that only your authorized users are sending emails on behalf of your domain:

But just how popular is DMARC? Mimecast reports in their report The State of Email Security 2022 that nearly nine in 10 companies (89%) are either using DMARC or plan to do so over the next 12 months. This is according to their global survey of 1,400 IT and cybersecurity professionals from 12 countries.

Of course, you can take DMARC a step further and bring your organizations digital identity to the next level. You can do this by integrating brand indicators for message identification (BIMI) and verified mark certificates (VMCs) in your organizations email digital identity. Doing this will enable you to insert your organizations verified logo into all of your organizations outbound emails from legitimate senders.

Running an outdated or unpatched version of your servers software is a surefire recipe for disaster. Patches are a publisher or developers way to fix bugs and other issues that leave your email servers vulnerable. If you dont apply those patches in a timely manner, you run the risk of cybercriminals exploiting these vulnerabilities to gain access to your email server(s) and data.

Something youll need to choose is how you want to implement updates. Do you want to handle them manually? Do you want to explore the option of automation? Each approach has its pros and cons, but the point is that you need to ensure that updates and patches dont fall between the cracks and dont find yourself facing another Eternal Blue situation.

(Quick explanation: Eternal Blue was a vulnerability in legacy Windows systems that Microsoft issued a patch for but organizations neglected to roll out in a timely manner. The end result was hundreds of thousands of devices globally being infected by ransomware in an attack that impacted hundreds of millions of people [if not more].)

Alright, were more than half way through our list of secure email server best practices. Much like how network firewalls operate, email server firewalls filter inbound and outbound traffic based on the rules on your email server. What this does is help you to keep tabs on incoming and outgoing communications on your domain to look out for any suspicious activities.

Of course, we cant give you any specific directions about setting up rules on your email server since every system is different. So, youll need to refer to your specific firewall manufacturers site for specifics on how to accomplish this goal.

While its important to monitor your traffic, youll also want to be sure to restrict both the number of emails that can originate from your domain as well as their sizes. A spike in outbound messages could indicate that one or more of your authorized accounts could be compromised and is being used to send spam or phishing messages. Setting rate limits can help protect your domains reputation.

Weve said it before and will continue to say that not everyone needs access to everything. This is true regarding everything from customer and employee database info to privileged access to your email servers. This is where access management best practices come into play.

You can set employee profiles so that users have only the minimal level of access they need to do their jobs. If someone needs access to a sensitive system for a project, assign them permission for the amount of time necessary to complete it. Be sure to remove those privileges once that access is no longer necessary (e.g., when they complete the project).

Furthermore, be sure to have a procedure in place that ensures access is revoked for accounts when employees leave your organization. Attackers or even disgruntled former employees love to use old logins to nose around systems they should no longer have access to. You can prevent this from occurring by deactivating their accounts right away.

As an administrator, you likely use secure shell (SSH) to manage your organizations various servers. Traditionally, this requires using a username and password combination for authentication. But theres a better (and more secure) way of doing that than relying on potentially weak login credentials: you can use public-private key pairs instead.

This method of authentication involves using cryptographic keys to prove your digital identity as a legitimate authorized user. One of which is public and the other your device keeps private that proves youre you. This process enables you to authenticate easily and securely without ever having to remember a cumbersome password.

Weve talked at length about the importance of SSH key management best practices previously. To quickly recap, SSH key management is about securing your cryptographic keys as part of your SSH access management strategy and security practices. (Be sure to check out the article linked at the beginning of this paragraph for more in-depth information.)

Protecting account credentials isnt optional; its the responsibility of every individual employee and network user. Why? Because compromising users accounts is the easiest way for hackers to compromise your server. Part of this approach to hardening your organizations cyber defenses involves educating and training users on cyber security best practices.

Some of the things effective cyber awareness trainings should cover include:

To help prevent your employees especially admins and other privileged user from falling for credential phishing scams, require everyone to digitally sign their emails. By adding a cryptographic digital signature (i.e., a signature thats verified by a public CA) to your email, youre doing two big things:

You can also use these certificates to encrypt emails containing sensitive data for added measure. This process requires both parties (sender and recipient) to have email signing certificates, and for the email sender to use the recipients public key. You then use their public key to encrypt the email before pressing Send and they use their corresponding private key to decrypt the message on their end.

If this sounds complicated, dont worry all you have to do is ask the recipient to send you a digitally signed email first. This way, you have a copy of their public key readily available. Its that simple.

Frankly, there are many reasons why implementing these email server security best practices is crucial for businesses and other organizations globally. The biggest reason is that its the right and responsible thing to do. Your customers, users and other stakeholders are entrusting you to protect their data.

Second, it helps to protect your interest by keeping your data secure from prying eyes. Cybercriminals or even your competitors would love to get their hands on the digital goodies you have stored on your email server.

Here are a few other quick reasons why having a secure email server is essential for your organization:

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10 Email Server Security Best Practices to Secure Your Email Server - Hashed Out by The SSL Store