Email Security Best Practices to Protect Your Business

A staff member receives an email that looks exactly like a message from a regular supplier. It asks them to update the bank account for the next payment. They do, and the money is gone before anyone notices anything was wrong.

Scenarios like this start with email, because email is where attackers reach your people directly. A single convincing message can hand over your logins, your client data, or a real payment.

The reassuring part is that most of these attacks are stopped by the way your email system is configured. The right email security best practices filter out the bulk of threats long before anyone has to make a judgement call.

This guide walks through the email security best practices every NZ business should have configured, what each control does, and how to tell whether yours are actually switched on. The aim is a clear checklist you can take to whoever manages your IT.

What Are Email Security Best Practices?

Email security best practices are the set of technical controls and policies that protect an email system from threats such as phishing, malware, spoofing, and account takeover. They work together to keep malicious messages out of inboxes and to limit the damage if one gets through.

These controls sit in two layers. The first is the filtering and scanning that inspects every message arriving at your domain. The second is the authentication and access settings that prove a message is genuine and stop attackers using a stolen password. Strong email security depends on both layers being in place, not just one.

For a business owner, the practical point is simple. Sound email security best practices are something you set up once and maintain, rather than something your team has to fight off message by message every day.

Why Is Email Still the Main Target?

Email is the main target because it reaches every employee and relies on human trust. Attackers do not need to break through a firewall when they can simply ask someone to click a link or approve a payment.

Attackers have also become far more convincing. AI now writes clean, personalised messages that copy a real supplier or manager, which is why phishing scams are harder to spot than the clumsy attempts of a few years ago. Configuration matters more than ever because you can no longer assume staff will catch every fake.

This shift is the core reason email security best practices have moved from a nice-to-have to a baseline requirement. When the human eye can no longer be relied on to spot a fake, the technical layer has to carry more of the load.

Which Email Security Best Practices Should Every Business Configure?

Every business should configure six core email security best practices: email filtering, anti-phishing protection, SPF, DKIM and DMARC authentication, multi-factor authentication on email accounts, link scanning, and attachment sandboxing. Together these cover the most common ways email is used to attack a business.

The list below is the practical baseline. A business with all of these configured correctly blocks the large majority of email threats automatically:

• Email filtering to remove spam, malware, and scam messages on arrival.
• Anti-phishing protection to catch impersonation and business email compromise.
• SPF, DKIM, and DMARC records to prove your mail is genuine and stop spoofing.
• Multi-factor authentication on every email account.
• Link scanning to check where a link actually leads.
• Attachment sandboxing to test files before they reach the inbox.

The sections that follow explain each of these email security best practices, what it protects against, and how to confirm it is switched on.

What Does Email Filtering Do?

Email filtering inspects every incoming message and blocks or quarantines anything that looks like spam, malware, or a scam. It is the first line of defence and removes a large volume of junk and dangerous mail before it ever reaches a person.

Modern filtering does more than match known spam. It scores messages on sender reputation, content patterns, and behaviour, so it can catch threats it has never seen before. Tuning the filter so that genuine mail still gets through cleanly is one of the email security best practices that takes a little setup work to get right.

How Does Anti-Phishing Protection Work?

Anti-phishing protection looks specifically for messages that try to impersonate a trusted person or brand to trick the reader into acting. It checks for spoofed display names, lookalike domains, and the language patterns common in fraud attempts.

When the system spots a likely impersonation, it can warn the reader, strip the message, or hold it for review. This control directly targets business email compromise, where an attacker poses as a manager or supplier to redirect a payment, which causes the largest financial losses for NZ SMEs. That is why it sits near the top of any list of email security best practices.

What Are SPF, DKIM, and DMARC?

SPF, DKIM, and DMARC are three records you publish for your domain that let other mail servers confirm a message really came from you. Without them, attackers can send mail that appears to come from your business, and your own messages are more likely to land in spam.

SPF lists which servers are allowed to send for your domain. DKIM adds a signature that proves a message was not tampered with. DMARC tells receiving servers what to do when a message fails those checks, and reports back so you can see who is trying to spoof you. All three should be configured and set to enforce, not just monitor, as a core part of your email security best practices.

How Do Access Controls Strengthen Email Security?

Access controls strengthen email security by making a stolen password far less useful to an attacker. Even strong filtering cannot help if someone gets your login, so protecting the account itself is just as important as the email security best practices that protect the inbox.

Why Is MFA Essential on Email Accounts?

Multi-factor authentication is essential because it stops an attacker logging in with a stolen password alone. They would also need the second factor, such as a code or an approval on your phone, which they almost never have. Turning on multi-factor authentication is the single highest-impact of all the email security best practices most businesses can put in place.

MFA should be required on every email account without exception, including senior staff and shared mailboxes. Attackers specifically target the accounts that are left out, and the owner or director is often the one who asked to skip it. A single uncovered mailbox can undo the protection on all the others.

How Should You Manage Account Access?

Account access should follow the principle of least privilege, meaning each person can only reach the mailboxes and data their role requires. Old accounts for departed staff should be disabled promptly, and admin access to the email system should be limited to a small, named group. These access habits are email security best practices in their own right.

These habits matter because a compromised mailbox is often the first step into the wider network. Tightening email access is part of treating every account and device as a potential entry point, not an isolated inbox.

What About Links and Attachments?

Links and attachments are the two parts of an email most often used to deliver an attack, so both need dedicated protection. Link scanning and attachment sandboxing are the email security best practices that check these elements at the moment they could cause harm rather than trusting them on arrival.

How Does Link Scanning Protect Staff?

Link scanning checks the destination of a link, often at the moment it is clicked rather than only when the message arrives. This matters because attackers frequently activate a malicious page only after the email has passed the initial filter.

When a link leads somewhere dangerous, the system blocks it and shows the user a warning instead of the harmful page. This protects staff even when a message looks completely legitimate and the link has been disguised, which is why link scanning belongs in any set of email security best practices.

What Is Attachment Sandboxing?

Attachment sandboxing opens a file in an isolated environment to watch what it does before delivering it to the recipient. If the file tries to install software or behave maliciously, it is blocked and never reaches the inbox.

This catches new threats that signature-based scanning misses, because it judges a file by its behaviour rather than by whether it has been seen before. For businesses that regularly receive documents from clients and suppliers, sandboxing is one of the email security best practices that closes a common gap.

What Are the Most Common Email Security Mistakes?

The most common email security mistakes are leaving accounts without multi-factor authentication, setting authentication records to monitor rather than enforce, and assuming the default platform settings are enough. Each of these leaves a gap that attackers actively look for.

Another frequent mistake is treating email security best practices as a one-time project. A common example is a mailbox that an attacker quietly sets to forward copies of every email to an outside address, sitting unnoticed for months. Settings that were correct a year ago can fall out of date as staff join and leave and the platform changes its defaults, and without a regular check, protection erodes without anyone noticing.

Why Are Default Settings Not Enough?

Default settings are not enough because they are built for the average customer, not for your specific risk profile. Common platforms ship with basic protection switched on, but the stronger anti-phishing, link scanning, and sandboxing features often need to be enabled and tuned deliberately.

Relying on defaults also tends to leave authentication records incomplete. Many businesses have SPF set up but never finish DKIM and DMARC, which means spoofing protection is only partly in place. Closing that gap means completing all of the email security best practices, not only the ones that are quick to switch on.

How Do You Avoid Blocking Genuine Mail?

You avoid blocking genuine mail by tuning your filtering and authentication carefully and reviewing quarantined messages during setup. Overly aggressive rules can hold legitimate client and supplier mail, which frustrates staff and tempts them to switch protection off.

Good configuration balances security with reliable delivery. This tuning, which keeps real mail flowing while blocking threats, is one reason email security best practices are worth setting up with experienced help.

How Do You Put These Email Security Best Practices in Place?

You put these email security best practices in place by auditing your current setup, fixing the highest-impact gaps first, and then maintaining the controls over time. The order matters because some controls deliver far more protection per hour of effort than others.

A sensible sequence starts with multi-factor authentication, since it blocks the most damaging attacks for the least effort. From there you complete your authentication records, confirm filtering and anti-phishing are tuned, and finally add link scanning and attachment sandboxing.

What Does It Cost to Improve Email Security?

Improving email security costs far less than most owners expect, especially measured against the cost of a breach. A single redirected invoice or a few days of downtime can cost more than years of proper protection. Several of the strongest controls, including MFA and authentication records, are included in plans businesses already pay for and simply need configuring.

The main investment is the time to set the controls up correctly and the ongoing attention to keep them current. For most NZ SMEs, putting proper email security best practices in place is a modest cost that removes a large and constant source of risk.

Should You Manage Email Security In-House or Outsource It?

Whether to manage email security in-house or outsource it depends on your team and capacity. Businesses with skilled internal IT can maintain these controls themselves, while many SMEs find it more reliable to have a provider configure and monitor them. A managed cyber security service keeps the settings enforced and up to date so they do not drift.

The right answer is the one that gets every control switched on and kept that way. An uncovered mailbox or an expired record undermines the whole system, so the controls need to stay in place long after the initial setup.

How Do You Keep Email Security Working Over Time?

You keep email security working by reviewing the controls regularly, updating them as threats change, and pairing the technology with staff awareness. These email security best practices are not a one-off task, because attackers adapt and business setups drift over time.

Technology stops most threats, but the people using the system are the final layer. Ongoing security awareness training helps staff recognise the small number of sophisticated messages that slip past the filters, so your team can catch what the technology misses.

How Often Should You Review Your Settings?

You should review your email security settings at least quarterly, and after any major change such as a new email platform, a merger, or a domain change. A review confirms that filtering rules, authentication records, and MFA coverage are all still correct and enforced.

Many businesses set controls up correctly and then drift as staff and systems change. Pairing strong email habits with broader endpoint security means a compromised mailbox is less likely to become a route into the rest of your network.

Get Your Email Security Best Practices Configured Properly

If you are not certain that filtering, authentication, MFA, and sandboxing are all switched on and enforced across your business, the safest assumption is that there is a gap. Exodesk helps Christchurch and Dunedin businesses put email security best practices in place and keep them secure as threats evolve.

Contact us today to discuss how we can help your business or connect with us on LinkedIn to stay updated with more insights.

Frequently Asked Questions

What are email security best practices?

Email security best practices are the configuration steps and policies that keep threats like phishing, malware, and account takeover out of a business inbox. The core practices are email filtering, anti-phishing protection, SPF, DKIM and DMARC authentication, multi-factor authentication, link scanning, and attachment sandboxing. Together they block most attacks before staff ever see them.

What is the most important email security control?

Multi-factor authentication on every email account is the single most important control. It stops attackers logging in with a stolen password, which is one of the most common ways businesses are breached. It is also quick to enable and works alongside filtering rather than replacing it.

What are SPF, DKIM, and DMARC?

SPF, DKIM, and DMARC are domain records that prove your email is genuine and stop others spoofing your business. SPF lists your approved sending servers, DKIM signs messages so tampering is detected, and DMARC sets the rule for what happens when a message fails those checks. All three should be configured and set to enforce.

How does email filtering work?

Email filtering inspects every incoming message and blocks or quarantines anything that looks like spam, malware, or a scam. It scores messages on sender reputation, content, and behaviour, so it can catch threats it has not seen before. Good filtering removes most dangerous mail before it reaches a person.

Can email security stop all phishing?

No single control stops every phishing attempt, but layered email security blocks the large majority automatically. Filtering and anti-phishing protection catch most fakes, while link scanning and sandboxing handle the dangerous parts of those that get through. Staff awareness covers the small number of highly targeted messages that remain.

What is attachment sandboxing?

Attachment sandboxing opens a file in an isolated environment and watches its behaviour before delivering it. If the file tries to act maliciously, it is blocked and never reaches the inbox. This catches new threats that traditional signature-based scanning would miss.

How is email security different from staff training?

Email security is the technical configuration that blocks threats automatically, while staff training prepares people to handle anything that slips through. Email security best practices do the heavy lifting because they stop most attacks without relying on a human decision. A business needs both layers to be well protected.

How often should email security settings be reviewed?

Email security settings should be reviewed at least quarterly and after any major change to your systems or domain. A review confirms that filtering, authentication records, and MFA coverage are still correct and enforced. Settings often drift as staff and platforms change, so regular checks prevent quiet gaps.

Is built-in email protection enough for a business?

Built-in protection from common email platforms is a reasonable starting point but is rarely enough on its own. Most businesses need additional anti-phishing, link scanning, and sandboxing layers, plus correctly configured authentication records. The default settings also tend to leave gaps that need tuning for your specific setup.

Can a managed IT provider handle email security?

Yes, a managed IT provider can configure, monitor, and maintain all of these email security best practices for you. This is often the most reliable approach because it keeps settings enforced and up to date as threats change. Exodesk supports Christchurch and Dunedin businesses with email security setup and ongoing management.