8 email security best practices for IT teams

Email remains the most heavily used business communication channel, and one of the most heavily targeted. From phishing and ransomware to social engineering and brand impersonation, attackers rely on email because it works. In fact, over 90 percent of successful cyberattacks begin with email. 

In a recent webinar featuring Exclaimer's InfoSec Manager Alex Dennis and Senior Product Marketing Manager James Wayne, they focused on how IT professionals can strengthen email security. They covered the full picture, from technical protocols and user training to the overlooked vulnerabilities hidden in something as basic as an email signature. 

Here are 8 best practices you need to know, why they matter, and how to take action. 

1. Recognize email as the weakest link in the security chain, and treat it accordingly 

Despite investments in network security, firewalls, and endpoint protection, attackers still choose email. It’s low-cost, scalable, and allows for highly personalized social engineering. The success rate is disturbingly high at around 3-5% globally. 

Today’s phishing attacks rarely have the broken English or suspicious attachments that were used in previous years. They’re crafted to look like internal workflows — an invoice from finance, a password reset from IT, a message from the CEO asking for urgent help. They often use accurate formatting, familiar branding, and names your team knows and trusts. 

These attacks are “designed to pass the eye test,” especially when employees are moving quickly, distracted, or on the move. And attackers don’t need access to your servers. They just need access to your people, with email being the easiest way to reach them. 

2. Protect email signatures – they matter more than you think 

When teams think about email security, they often focus on infrastructure. But the message content and visual structure of an email, including the signature, also play a role in building or breaking trust. 

An email signature might seem like an afterthought. But when it’s inconsistent, unmanaged, or editable by users, it presents an opportunity for cyberattacks. 

When you lose control of how your organization presents itself, you open the window for spoofing, brand manipulation, and compliance issues. 

Here’s where unmanaged email signatures create problems: 

• Spoofed emails are easier to execute when attackers can replicate your signature formatting. 

• Inconsistent branding across departments makes phishing harder to detect internally. 

• Manual editing by users introduces the potential for errors and outdated information. 

• Missing legal disclaimers can lead to regulatory violations in sectors like finance or healthcare. 

• Legacy templates still in circulation can misrepresent your organization externally. 

For example, a phishing attempt that includes a cloned signature from a real employee may slip through undetected if that employee’s legitimate signature varies slightly each time. 

This inconsistency makes it harder for both recipients and your own teams to detect anomalies, which ends up undermining your security posture. 

3. Use signature control to support compliance and brand governance 

Beyond security, consistent email signatures are essential for legal and brand reasons. Many organizations operate under strict regulatory standards. Inconsistent disclaimers, missing statements, or outdated information can open you up to fines and legal challenges. 

From a brand perspective, badly formatted or off-brand signatures reflect poorly on your organization’s professionalism and credibility. Customers, partners, and vendors draw conclusions about your company based on every communication. 

Centralized email signature management helps you keep control, distribute updates automatically, and support both security and compliance initiatives. 

4. Train your people - human behavior is still the biggest risk 

Technology can catch a lot of threats. But it can’t stop someone from clicking a link in a convincing-looking email. 

No matter how sophisticated your tools are, your people are still vulnerable to deception, especially when threats are disguised as everyday communications. This includes fake messages from trusted vendors, impersonated colleagues, or urgent requests that bypass protocol. 

To reduce human error, you need ongoing training and a culture of caution. That includes: 

• Phishing simulation campaigns that test users and reinforce learning 

• Guides or infographics on what legitimate emails should look like 

• Encouraging a verify-first culture, where employees ask before responding to unusual requests 

• Highlighting real examples of spoofed emails, especially those that mimic internal communications 

When users know what normal looks like, including the correct email signature format, language, and tone, they’re more likely to question messages that deviate from that norm. 

5. Be aware that threat actors now target your domain, not just your devices 

Cyberattacks used to focus on breaking into your infrastructure. Now, many threats focus on using your organization as a disguise. Attackers impersonate your brand to deceive customers, partners, and even internal stakeholders. 

This kind of impersonation, often referred to as business email compromise (BEC), can involve: 

• Registering lookalike domains, e.g. using “rn” instead of “m” to mimic a real name 

• Spoofing internal sender names in messages to trick employees into wiring money or sharing credentials 

• Using compromised vendor accounts to target your team in a supply chain attack 

The moment someone outside your business receives a fake email that looks like it came from you, your reputation takes a hit. This means it’s no longer enough to filter inbound threats. You also need to protect how your messages are received and perceived externally. 

6. Use SPF, DKIM, and DMARC to protect your identity 

These three email authentication protocols form the foundation of email trust. Without them, attackers can spoof your domain and impersonate your brand. 

• SPF (Sender Policy Framework) defines which mail servers are authorized to send messages on your behalf. 

• DKIM (DomainKeys Identified Mail) attaches a digital signature to your email header that validates the content hasn’t been changed. 

• DMARC (Domain-based Message Authentication Reporting and Conformance) tells receiving servers what to do if an email fails SPF or DKIM checks and sends reports back to your team. 

When these protocols are implemented and monitored correctly, they significantly reduce the risk of impersonation. However, partial implementation or misconfiguration can lead to gaps. 

A common issue is when organizations set up SPF and DKIM but leave DMARC in “none” mode. This means no action is taken on failed messages. 

DMARC should be moved toward a “reject” policy once you have visibility through reporting. That gives you active protection and insight into who’s sending email using your domain. 

7. Be ready for email threats that target departments differently 

Email-based threats don't affect every department the same way. Legal, HR, Marketing, and Compliance will all face their own unique risks. For example: 

• Legal teams receive phishing emails disguised as contracts, subpoenas, or regulatory updates 

• HR teams are targeted with malicious CVs or fake onboarding materials 

• Marketing may be hit during campaigns or product launches with impersonation attempts or link injection 

• Compliance teams face urgent requests designed to bypass approval workflows 

These attacks are believable because they reflect familiar routines. The attackers know what each department expects to see, and they mimic it.  

That's why email security policies need to include more than generic instructions. It needs to include security training and alerts that are tailored to the context of each team. HR needs to know what fake CVs look like. Legal needs to know when a document looks suspicious. Marketing needs to recognize when a sender’s domain is off by a character. 

While IT will take the lead, equipping every department with relevant knowledge strengthens the whole organization’s security posture. 

8. Build a proactive, adaptable email security program 

Email threats evolve constantly. So should your strategy. Here's just a few practical cadences you can use to stay ahead of these risks: 

• Quarterly policy reviews to address new threats, business changes, and align IT, legal, HR, and marketing policies.  

• Implement email signature management for consistency, branding, and legal compliance.  

• Audit email signatures and domain security by reviewing domain reputation and optimizing SPF, DKIM, and DMARC configurations.  

• Monitor DMARC reports to identify misuse or anomalies.  

• Run phishing simulations and user training to address emerging social engineering trends.  

• Review email security metrics like bounce rates, phishing test outcomes, and user-reported incidents to refine your program. 

The more visibility and accountability you build into your security processes, the stronger your defense will be. 

Every email reflects your organization 

Whether it’s a cold outreach, an internal request, or a reply to a customer, every message you send represents your business. Attackers know this. That’s why they work so hard to exploit email as a trusted channel. 

Protecting your email environment needs to be more than filter threats. You need to proactively manage how your organization presents itself in every message, from sender verification to the email signature.  

Watch the full webinar to discover how to strengthen your email security strategy and regain control.