Email Security Best Practices: Safeguarding Your Digital Communication

Email is a primary channel for communication and collaboration in the workplace. 

It also remains the top vector for cyberthreats. 

Most organizations, small and large, now use cloud-based email platforms. While they provide basic, built-in, email hygiene solutions, these often fall short in today’s rapidly changing, and AI powered, email threat landscape. That leaves many organizations vulnerable to compromise through the most common way people outside your organization communicate with your users. 

Email security isn’t a binary measure—it’s not a matter of simply turning it on and being protected. Implementing a solution doesn’t necessarily limit your risk of compromise. Effective email security for businesses calls for adopting the right set of technologies and operational procedures, plus making sure your users understand the risks and know what to look out for, to achieve the most complete protection. 

In this article, we examine email security best practices that will allow you to better protect your users, clients, and businesses from modern cyberthreats. 

Table of Contents

• Understanding the Importance of Email Security
• Critical email security threats 
• Top 10 Email Security Best Practices  
  • 1. Enforce DMARC, SPF, and DKIM
  • 2. Deploy AI-powered threat detection
  • 3. Implement phishing awareness training
  • 4. Implement AI-powered recipient validation
  • 5. Establish continuous email access
  • 6. Secure hidden entry points
  • 7. Adopt phishing-resistant Multifactor Authentication (MFA) 
  • 8. Automate email encryption
  • 9. Enforce legally compliant, automated archiving
  • 10. Centralize Multi-Tenant Management (For MSPs/Large Orgs)
• Things to Consider when developing your email security policy
• Don’t Just Secure Your Email—Transform It 
• Conclusion & FAQ

Understanding the importance of email security 

Gone are the days when the Nigerian Prince scam characterized the quality and sophistication of most email threats. The infamous phishing attack symbolized an age when threats were indiscriminate and easily spotted compared to today’s standards. 

AI-Powered Phishing At Scale

The modern threat landscape has drastically changed to deploy highly advanced, convincing, and targeted attacks at scale. Easy access to powerful LLMs fuels this process. These models ensure spelling, grammar, and tone are perfect. They also customize email content for each recipient. This customization increases the chance of “success”.

Tactics Behind Modern Attacks

Phishing emails use personalized information and abuse legitimate services to make attacks harder to detect while appearing more credible. Business Email Compromise (BEC) scams leverage in-depth research on a victim. They use details about the victim’s current role or background to coerce them. Cybercriminals may also use compromised accounts to hijack existing email threads. Additionally, they impersonate legitimate senders and distribute threats. This approach preys on trusting targets.

The Rising Cost Of Breaches

The lines between malicious and legitimate content can seem indistinguishable. Unlike the days of the Nigerian Prince, hackers are engineering campaigns that are far more convincing and targeted. And the results show. The cost of a data breach has reached an all-time high, averaging $4.4 million (USD) globally, according to IBM Cost of a Data Breach Report 2025. For businesses with 500 or fewer employees, that figure totals $3.31 million (USD). 

Critical email security threats 

While several types of email security threats exist, below are the most common and concerning types: 

• Phishing: Phishing is a common email security threat where attackers impersonate well-known, established brands to deceive recipients into clicking malicious links or downloading malware-laced attachments. It is a common type of attack that targets multiple mailboxes and lacks any personalization in the content for the recipients. Phishing can result in credential harvesting, malware infections, account takeovers (ATO), and more.
  
  It remains the most effective cyberthreat by victim count, according to the Internet Crime Complaint Center. The IC3 received 859,532 complaints from victims in 2024 alone. Meanwhile, Hornetsecurity has detected a record number of phishing threats in 2025.
  
• Quishing: A common variant of Phishing is “Quishing”, or QR code phishing where the malicious email contains a QR code instead of a link. Well trained users are vary of links, but they are used to scanning QR codes to pay for parking, access menus in restaurants etc. An added benefit for the attacker is that the user will use their smartphone to scan it (often a personal device, with less protection / policies applied than a work laptop) and thus move the attack to a device where the attack is more likely to succeed.
• Spear phishing or BEC: Spear phishing, often referred to as Business Email Compromise (BEC), is a highly targeted cyberattack. Spear phishers impersonate a legitimate person or vendor known to the victim.
  
  Spear phishing attacks don’t usually contain malicious links or attachments, especially in the first email. Rather, they use textual content, research on a victim, and social engineering techniques to manipulate their intended targets into taking a compromising action, usually financial in nature. This includes:
  
  – transferring funds to a fraudulent account (wire transfer fraud),
  – sending tax documents to hackers (tax fraud or W2 fraud), 
  – purchasing gift cards in bulk (gift card fraud), and more. 
  
  This flavor has become very powerful because of Generative AI such as ChatGPT being able to finetune the language, and AI agents being able to automate many of the steps, leading to increased scale of customized attacks.
   
  Spear phishing attacks are the costliest cyberthreat. Reported damages from BEC reached $2.77 billion (USD) in 2024, according to the IC3. Equally concerning, the number of BEC attacks continues to climb. According to the Verizon’s Data Breach Investigation Report 2025, BEC attacks caused more than $ 6.3 billion in damages in 2024. 
• Email-based malware: While malware poses a threat from several vectors, email remains the top channel for distributing it, including ransomware. This type of email threat typically uses an attachment containing malware that infects the victim’s device once downloaded. Malware-laced attachments most often take the form of Microsoft Office documents, according to Verizon. Some email-based malware attacks may instead contain a malicious link that redirects the victim to a phishing page, which delivers the payload.
• Attacker-in-the-middle (AitM) attacks: AitM attacks occur when hackers intercept or eavesdrop on communications between two legitimate parties. A common AitM attack occurs when hackers apply phishing techniques to harvest credentials from victims. This is now a standard feature of the “all in one” phishing kits that attackers can subscribe to in dark web marketplaces, and it usually involves a phishing email with a link to a AitM page.
  
  The user is tricked into clicking the link by a lure (“you need to reset your password”, or “login here to access your voicemail”), and when they do they see a page that looks exactly like their normal sign in page. As they’re entering their username and password these are passed to the real login page, and if there’s a Multi Factor Authentication (MFA) challenge such as a two-digit code, this will be passed back to the user to complete the login. The attacker has now captured everything they need to impersonate the real user and will proceed to further compromise data and systems from here.  
• Spam: Spam is unsolicited and often unwanted emails sent in bulk to many recipients. While spam doesn’t inherently have malicious intent, it clutters mailboxes, consumes network resources, and delivers malicious content, including phishing links.

Top 10 Email Security Best Practices  

As mentioned previously, secure and effective email security calls for the right set of solutions and operational procedures. To strengthen your posture, adopt the best practices below and make them an ongoing priority for your business. 

1. Enforce DMARC, SPF, and DKIM

There are three main email security protocols that email servers use to verify incoming emails, Sender Policy Framework (SPF), Domain-based Message Authentication, Reporting, and Conformance (DMARC) and DomainKeys Identified Mail (DKIM).

Together they allow email servers to determine if an incoming email has been sent from an authorized server for that email domain, that it hasn’t been tampered with in transit, and what to do with it if fails any of the checks. It’s a way to minimize spam and phishing emails that purport to come from someone you trust but is actually fake.

Use our DMARC Manager to ensure that you’ve set these correctly. This applies to your main business email domain(s). It also includes any testing or unused email domains you own.

2. Deploy AI-powered threat detection

When selecting an integrated email hygiene solution, make sure it’s not relying on signature-based filters. This legacy way of blocking malicious emails can’t keep up with the modern world of highly personalized, AI-powered malicious emails.

It takes too long to identify a particular malicious email, then push out the signature to catch subsequent incoming emails. Instead, you need Advanced Threat Protection (ATP) for email security. It uses AI and Machine Learning (ML) models. These models analyze all characteristics of each email. They evaluate the text to determine if it’s malicious, spam, or legitimate.

For attachments, you need a Sandbox that opens each attachment (“detonates”) in an isolated environment, and again looks at how the file / document behaves to render a verdict – safe or malicious.  

3. Implement phishing awareness training

No individual solution is 100% effective, attackers are always trying new tricks to bypass filters, which is why you need layered defenses so that attackers have to clear several hurdles before they reach their goal.

Build Your Human Firewall

Part of email security best practices are your users, if all other layers have been bypassed you want your users to be “politely paranoid”. But the “once a year, mandated 1/2hr course” isn’t going to suffice, you need a modern solution such as Security Awareness Service (SAS), which sends simulated phishing emails regularly, and when users fall for them, short training is provided.

This regular reminder training provides a much better recall for your users and makes it more likely that they’ll spot a scam and report it.  

How SAS Adapts Automatically

SAS is AI powered and has one feature that’s loved by administrators, it’s pretty much set and forget. Users who need additional testing and training in a particular area are automatically given it, whereas already careful users aren’t sent simulated phishing emails very often.

Building your human firewalls to be stronger does tend to make them report more emails to your Security Operations Center (SOC) staff, so our AI Email Security Analyst helps out here as well, automatically checking each reported email to see if it’s really malicious or not.

4. Implement AI-powered recipient validation

The most common reason for inadvertent data leaks in businesses is sending emails with sensitive content to the wrong person. Autocompleting email addresses is convenient, but sometimes you end up sending the wrong thing to the wrong person(s), occasionally with catastrophic consequences. Here’s where a built in AI assistant / recipient validation can provide a warning and an extra check before that email is sent by mistake.

5. Establish continuous email access

Email is a “plumbing” service, invisible and taken for granted, just like phones and electricity supply. It’s only when it’s interrupted that we realize how much we rely on it. Having 24/7 emergency inboxes which activate automatically if your Microsoft 365 tenant goes down helps ensure business continuity.  

6. Secure hidden entry points

Modern collaboration, both internally and externally, is multifaceted, it’s not just email anymore. Microsoft Teams is used for phone calls, chats and meetings and provides attackers with another avenue of reaching your users which is often not as well protected as email is. Add links in SharePoint and third-party messaging tools and there are more attack vectors than ever.

Total Protection Plan 4 includes Teams Protection which scans all links shared in Teams and warns end users when they lead to malicious destinations.

7. Adopt phishing-resistant Multifactor Authentication (MFA) 

Why MFA Matters

Like effective password policies, MFA makes it harder for hackers to compromise and manipulate legitimate accounts. MFA requires users to authenticate their identity through multiple factors before accessing email or other applications.

Choosing Stronger MFA Options

However, not all MFA is created equal as we saw earlier with AitM attacks, so you’ll want to roll out phishing-resistant MFA to all users. This includes FIDO (Fast IDentity Online) USB hardware keys, Windows Hello for Business (Windows), Platform Credentials (MacOS) and the newest type, Passkeys. This is the same as a FIDO key but uses a smartphone instead of a separate USB hardware key.

Why Phishing Resistance Matters

These are called phishing resistant MFA because they don’t work on a fake login page, even if the user thinks it looks authentic, thus protecting the user in scenarios where they have been tricked. However, the devil is in the detail, the aforementioned phish kits that attackers use also include (as a standard feature) the automatic downgrade of the login type, so that if you allow it, instead of being prompted for the phishing resistant MFA type, it’ll ask the user to perform a lower strength sign-in to satisfy MFA.

Thus, not only do you need to roll out phishing resistant MFA for all users, you also must set the policy to not allow other, weaker methods.

The Helpdesk Risk

Finally, don’t forget about the people aspect. Some threat groups have become very adept at social engineering, particularly against helpdesk staff, leading to some high-profile breaches. It doesn’t matter if you have the strongest MFA, rolled out for everyone, if the bad guys can just call up your help desk, convince them (with publicly available personal information) that they’re an IT admin in your organization who has lost their phone and laptop and get their credentials reset, allowing them access.

8. Automate email encryption

Why Email Encryption Matters

Business email contains a lot of sensitive data and is stored in distributed mailboxes for your whole organization, plus all the emails with sensitive data that have been sent to external recipients. The solution is email encryption which protects the confidentiality and integrity of your email communications.

These solutions make digital communications unintelligible to unintended recipients, who lack the decryption key. At a time when AitM attacks are increasingly common, encryption keeps correspondence and other information secure.

Automating Sensitive Email Protection

However, relying on end users to remember to manually encrypt a sensitive email or attachment isn’t a reliable governance strategy, even with the best intentions, human errors will occur. Thus, an automated policy (like the one in 365 Total Protection) which scans emails for sensitive data (IBAN, Social Security number etc.) and if found, encrypts the email automatically, ensuring that only the sender and recipient can access it.

9. Enforce legally compliant, automated archiving

Ensuring that email communication is kept safe and not tampered with for the retention period you’re legally required to, depending on the regulatory framework(s) you operate under, is crucial. Having an automated archiving solution in place ensures that you can access emails for audit purposes, even if a mailbox is compromised or deleted.  

10. Centralize Multi-Tenant Management (For MSPs/Large Orgs)

Many large enterprises end up with several Microsoft 365 tenants, often due to mergers and acquisitions, and many small businesses rely on a Managed Service Provider (MSP) for their IT support needs. In both scenarios, the overhead of keeping policies and settings in synch across tenants can be extensive.

The power of Hornetsecurity’s 365 Multi-Tenant Manager helps here. It lets you easily check each tenant’s current configuration against your templates, with automated remediation available if desired.

Things to Consider when developing your email security policy: 

• Create the policy using an existing template from a reputable organization, like the SANS Institute. 

• Make it easy for employees to locate and access the policy. 

• Make it digestible and easy to understand. 

• Incorporate the email security policy into new hire orientation and onboarding programs. 

• Promote the policy in formal and informal organizational meetings. 

• Allow employees to review and officially acknowledge the policy at the outset and whenever significant updates occur. 

As you can see, Hornetsecurity’s 365 Total Protection takes care of all aspects of email and collaboration security. It helps you navigate complex global regulations like GDPR and HIPAA while seamlessly fitting into your daily operations. Plus, it requires very little IT admin work!

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Don’t Just Secure Your Email—Transform It 

Is your organization still relying on manual checks and basic filters? Upgrade to a proactive posture that protects your brand, your data, and your users automatically. 

With 365 Total Protection, you get: 

• Total Peace of Mind: Automated DMARC management and AI-driven phishing protection. 

• Zero-Disruption Continuity: Keep your business running even during Microsoft 365 outages. 

• Effortless Compliance: Tamper-proof archiving and automated encryption that takes the burden off your employees. 

Your email deserves the best protection—check out 365 Total Protection! 

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Conclusion 

Relying on a trusted partner with industry-leading technology is essential for your email and collaboration security. With the support of our Security Lab, you can greatly enhance your chances of success.