Email security best practices to protect your business in 2025

Email serves as one of today's most critical communication channels, capable of delivering diverse and persuasive internal and external messaging at scale. Unfortunately, this channel is also uniquely vulnerable. For years, cyber attacks have plagued email communication, sparking data breaches and prompting huge financial losses.

Unfortunately, data suggests that these attacks are as dangerous as ever — and the use of email as an attack vector may be accelerating. Concerning insights from Verizon's Data Breach Investigations Report (DBIR) indicate that the human element (errors, social engineering, misuse) was involved in 60% of breaches, with phishing and credential abuse remaining the most common drivers of breaches, frequently initiated via email communication.

The takeaway? Most businesses need to implement far more robust email security. Thankfully, there are many straightforward solutions you can implement to prevent breaches while safeguarding both employees and consumers.

Keep reading to learn how Sectigo supports this effort via S/MIME certificates, VMC certificates, and automated lifecycle management.

What is email security and why it matters

Email security involves the wide range of tools, technologies, and methods used to safeguard digital communication against common concerns such as unauthorized access or data leaks. This is important because email represents one of the most significant vulnerabilities within modern digital infrastructure. This is a top target among sophisticated attackers, who aim to exploit a variety of weaknesses in order to access sensitive information.

In addition to protecting individuals and organizations against cyberattacks, email security is also critical from a compliance perspective. Regulations such as the GDPR and even the HIPAA mandate that strong safeguards capable of protecting sensitive information are implemented.

Top email security threats organizations should know about

Many threats are capable of derailing email communication while placing users and organizations at risk. Top areas of concern include:

• Phishing. Typically involving deceptive emails designed to trick users into sharing private information, phishing uses manipulative tactics to exploit victims' trust or perceived familiarity. While phishing can take many forms, email has long represented one of the most utilized methods, in part because its perception as a more professional type of communication channel means that users are more likely to regard phishing emails as authoritative or trustworthy. Spear phishing brings a more targeted approach to traditional phishing attacks, featuring customized messages that are even more likely to evade suspicion.

• Business Email Compromise (BEC). As a specific and uniquely dangerous form of phishing, BEC involves impersonations of legitimate businesses, with higher-level professionals such as CEOs frequently targeted. Verizon's latest DBIR insights suggest that this is one of the fastest growing vectors, capable of driving huge financial losses along with reputational damage.

• Malware and ransomware. Short for "malicious software," malware involves a wide range of software designed to harm devices, networks, or users. Ransomware is similar, but blocks access to critical files or systems until the victim pays the attacker a ransom. DBIR insights suggest that ransomware attacks are accelerating, with 44% of the past year's cybersecurity breaches involving this type of costly attack.

Proven business email security best practices for 2025

As attackers grow more sophisticated, there is less room for error, and unfortunately, safeguards that proved sufficient a few short years ago may no longer be enough to keep sensitive information safe. In 2025 and beyond, email security requires a strategically layered approach, in which several strategies coalesce to provide broad protection.

Essentials in 2025 include:

1. Enforce strong, unique passwords

Strong, unique passwords are essential, but certainly not sufficient on their own for preventing brute-force attacks and limiting unauthorized access. In 2025, this is absolutely non-negotiable, and yet, far too many businesses still neglect to implement sufficiently secure password requirements.

Best practices highlighted by the Cybersecurity and Infrastructure Security Agency (CISA) include the following:

• Passwords must be at least 16 characters long and include mixed-case letters, numbers, and symbols

• Use enterprise-level password managers or identity and access managers (IAMs)

• Implement single sign-on (SSO) where possible

2. Enable multi-factor authentication (MFA)

Multi-factor authentication provides a crucial layer of defense, going above and beyond simple passwords to build additional factors into identity verification. While this strategy, alone, cannot guarantee strong email security, it provides a solid starting point. Although this should be required for all accounts, it's particularly crucial for high-privilege access.

Biometrics can enhance MFA by using facial recognition or fingerprint scanning to make it more difficult for attackers to replicate key authentication factors. Many enterprises also favor hardware tokens, which can leverage cryptographic keys and may be less vulnerable to phishing attacks.

3. Utilize email encryption with S/MIME certificates

Email encryption ensures that only intended recipients can read messages, even if they are ultimately intercepted. If other security solutions fall short, this form of encryption should provide a much-needed safeguard.

This effort relies on S/MIME (Secure/Multipurpose Internet Mail Extension) encryption—X.509 digital certificates issued by a trusted CA—that leverage public-key infrastructure (PKI) to both encrypt and sign your email. When you compose a message, your mail client uses the recipient’s public key (embedded in their S/MIME certificate) to encrypt the content so that only their matching private key can decrypt it; at the same time, it applies a digital signature using your private key, which recipients validate with your public key to confirm the message truly came from you and hasn’t been tampered with.

4. Provide regular security awareness training

Even seemingly tech-savvy employees can be surprisingly vulnerable to sophisticated phishing attacks — especially spear phishing and BEC. Training can help professionals spot hidden signs of tampering, making them less likely to fall victim to common attack strategies. This also ensures that employees maintain necessary safeguards such as strong passwords or the consistent use of MFA.

5. Avoid accessing email on unsecured networks

Unsecured networks pose major security risks, in part because they frequently lack encryption. As a result, hackers may find it easier to intercept emails and gain access to sensitive information. This can also increase the risk of man-in-the-middle (MiTM) attacks, in which bad actors not only intercept sensitive data between the user and the server, but also, manage to alter that information without being detected.

Remote and hybrid workers may be tempted to use public WiFi, but this should be strongly discouraged. At minimum, users should rely on virtual private networks (VPNs) to reduce the likelihood of tampering.

6. Automate machine identity management and enforce access policies

Machine identity management (MIM) aims to secure and control the digital identities of the many devices that exist within the contemporary IT environment. Crucial elements of MIM include managing digital certificates and enforcing policies involving encryption and authentication.

Both essentials can be automated to boost efficiency and limit the potential for outages. In general, MIM supports a stronger security posture, which is crucial for safeguarding email communication. For this reason, MIM should be fully integrated with overarching IT infrastructure and security frameworks.

7. Automatically scan attachments and links

Email attachments and links are among the most commonly utilized vectors in today’s phishing campaigns, with manipulated email recipients triggering attacks by inadvertently downloading malicious content.

Because these can appear harmless even to discerning users, they must always be scanned to detect hidden malware or suspicious code. Sandboxing can elevate this effort, providing an isolated environment in which attachments or links can be analyzed without risking network integrity.

8. Implement Verified Mark Certificates (VMCs)

VMCs boost trust by prominently displaying identifiable logos within recipients' inboxes. This enhances overall security by encouraging users to verify message legitimacy before engaging with email content. Furthermore, VMCs promise additional benefits such as increased trust and engagement.

The process of obtaining VMCs involves an authentication protocol known as DMARC (Domain-based Message Authentication, Reporting, and Conformance). This incorporates p=quarantine or p=reject policies, which instruct servers to reject emails that do not pass strict standards.

9. Deploy advanced spam filters and secure email gateways

Spam filters can identify unwanted emails, including those believed to be malicious. Not just any spam filter will do, however; some rely on basic strategies such as keyword detection, and, as a result, are more likely to miss cleverly disguised threats that lack obvious red flags. In 2025, AI-powered filters are becoming more popular and offer more robust protection by adapting to reflect emerging threats quickly.

We've touched on the value of DMARC, but DKIM (DomainKeys Identified Mail) is just as valuable, as this uses digital signatures near outgoing emails' headers, making it easier to confirm that email messages were not altered in transit. Meanwhile, the SPF (Sender Policy Framework) protocol specifies the servers that are allowed to send emails so that spammers are less likely to forge messages.

10. Regularly update email clients and plugins

As new vulnerabilities emerge, these should be patched promptly to address known security flaws, which are otherwise likely to be exploited by bad actors. Meanwhile, software updates may unleash enhanced security features capable of combating emerging threats. Centralized platforms support this effort by automating and enforcing policy updates.

While updates can help, it is also important to consider the overall attack surface and how unused add-ons, extensions, or plug-ins might increase this. These should regularly be removed to limit the complexity of the enterprise environment while limiting potential cyberattack entry points.

Special considerations for small businesses

Small businesses face significant email security challenges, in part because they often lack the robust resources available to larger corporations. Some attackers have even been known to purposefully target SMBs for this very reason; they assume that these businesses will naturally have weaker security strategies and will therefore be easier targets.

Solutions such as S/MIME certificates can provide much-needed peace of mind but should be accompanied by a broader approach that encompasses MFA, patching, and regular employee training. Centralized platforms provide comprehensive oversight, automating email security and monitoring threats from a single, easy-to-access interface.

What to do if your email account gets hacked

Despite adopting the robust security strategies highlighted above, breaches remain a real risk and, at some point, it's likely that a uniquely sophisticated infiltrator will gain access. After all, many of today's most technologically advanced corporations have fallen victim to well-publicized data breaches and other attacks. With a proactive strategy, however, it's possible to minimize the damage and avoid downtime.

Any response plan should include these essentials:

• Alert and mobilize IT teams as soon as possible

• Enable MFA and reset all passwords.

• Inform any customers or stakeholders who may have been impacted.

• Review email logs to identify the attack vector and determine the scope of the breach.

• Monitor the IT environment closely for further suspicious activity.

Solidify your business email security with Sectigo

As cyber threats continue to evolve, enterprises will need to maintain a layered approach to email security that integrates cutting-edge tools and technologies. Robust security policies and strategies help businesses adapt alongside quickly evolving cyber threats. Any strategy for combating email hazards should include strong encryption and identity verification.

Sectigo is a leading provider of S/MIME certificates and digital identity solutions, offering powerful protection for email accounts. We also offer Verified Mark Certificates (VMCs), enabling organizations to display their brand logos in customer inboxes, improving brand trust while supporting overall email security. Combined with comprehensive certificate lifecycle management via Sectigo Certificate Manager (SCM), our solutions make it easy to manage, secure, and scale email communications.

Explore our encryption solutions today or see SCM in action.

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What are Verified Mark Certificates & how do they help authenticate emails?