Email Security Assessment for Phishing and Spoofing - Aegixis

Email remains one of the most trusted communication channels inside a business. According to Statista, around 376 billion emails are sent and received each day. Businesses use email to approve payments, exchange contracts, reset passwords, share documents, and communicate with customers and suppliers.

That trust also creates opportunities for attackers.

A convincing message can persuade an employee to disclose credentials, approve a fraudulent payment, open a malicious file, or grant access to a cloud application. If an attacker compromises a genuine mailbox, fraudulent messages can become even more convincing because they come from a real account and may continue an existing conversation.

An email security assessment examines the controls protecting an organisation’s domains, mailboxes, users, and email infrastructure. It helps determine whether attackers could impersonate the business, compromise accounts, bypass filtering, or maintain access after an initial breach.

A complete assessment goes beyond phishing simulations. It combines configuration review with controlled testing to show whether the organisation can prevent, detect, and respond to realistic email-based threats.

Why Email Attacks Remain So Effective?

Email attacks remain effective because they target both technology and human decision-making. An attacker does not always need malware. A message may direct an employee to a fake sign-in page, request a bank-account change, impersonate a senior manager, or continue a legitimate supplier conversation after compromising a mailbox.

Publicly available information makes these attacks easier to personalise. Employee names, job titles, supplier relationships, events, invoices, and social media activity can all help attackers create believable messages.

Technical weaknesses increase the risk. Poor domain authentication can make impersonation easier, while weak account protection may allow stolen credentials to be reused. Forwarding rules, application permissions, or active sessions can also help attackers retain access after a compromise.

Email security is therefore closely connected with identity security. A compromised mailbox may expose password-reset emails, internal documents, contacts, and information that supports further attacks. Where email access is linked to wider organisational accounts, businesses may also need to review their identity and privileged access controls.

What an Email Security Assessment Should Examine

A professional assessment should reflect the organisation’s actual email environment rather than rely on a generic checklist.

The review should consider the email platform, domain structure, authentication model, administrative permissions, third-party sending services, and the way employees use email for important business processes.

Domain Authentication and Sender Protection

The assessment should review SPF, DKIM, and DMARC to determine whether the organisation correctly authorises legitimate senders and handles unauthenticated messages appropriately. It should also consider subdomains, unused domains, third-party mail services, display-name impersonation, and lookalike domains. The presence of SPF, DKIM, or DMARC records alone does not mean the domain is protected. Administrators may misconfigure or inconsistently apply controls, while external services may weaken them.

Mailbox and Account Security

Assessors should evaluate mailbox protection alongside the organisation’s wider authentication controls. This includes multifactor authentication, password policies, session management, account recovery, legacy authentication, delegated access, shared mailboxes, administrative roles, and application permissions.

These controls need to work together. Multifactor authentication, for example, may provide limited protection if older protocols remain available or if an attacker can retain access through an existing session or malicious application.

Filtering, Monitoring, and Response

The assessment should also examine whether email systems and security teams effectively block, detect, and investigate suspicious messages. Email gateways and cloud platforms may inspect attachments, links, sender behaviour, impersonation attempts, QR codes, password-protected archives, and other suspicious content. Security teams also need useful logging, alerting, message tracing, and user-reporting mechanisms. The objective is not simply to confirm that administrators have enabled these features, but to determine whether they work when a realistic attack occurs.

Domain Spoofing and Impersonation Risks

Attackers often try to make fraudulent messages appear connected to a trusted organisation. They may spoof the real domain, register a visually similar domain, change the sender display name, abuse a third-party email platform, or compromise a supplier account. SPF, DKIM, and DMARC help receiving systems evaluate whether a message has been sent through authorised infrastructure and whether the authenticated domain matches the domain visible to the recipient.

However, these controls must work across every legitimate sender.

A business may use its main email platform alongside marketing tools, invoicing systems, recruitment platforms, support software, and other cloud services.  If administrators do not properly document those senders, they may avoid stronger DMARC enforcement because they are concerned about blocking legitimate email.

Common Email Impersonation Methods

Impersonation method	Example	Main control area
Direct domain spoofing	A message claims to come from the organisation’s real domain	SPF, DKIM, and DMARC
Lookalike domain	An attacker registers a similar spelling or character variation	Domain monitoring and user awareness
Display-name impersonation	The sender appears to be an executive or supplier while using an unrelated address	External sender warnings and impersonation protection
Compromised mailbox	A real account sends fraudulent instructions inside an existing conversation	Authentication, detection, and containment
Third-party sender misuse	A connected email platform is abused	Application and supplier security controls

Why Domain Authentication Alone Is Not Enough?

No single control prevents every type of email impersonation.

DMARC can reduce direct spoofing of the organisation’s own domain, but it cannot prevent attackers from registering a convincing lookalike domain. External sender warnings may help identify suspicious messages, but they are much less effective when an attacker is already using a genuine mailbox.

Effective protection therefore depends on domain authentication, filtering, monitoring, user awareness, and business verification processes working together.

Account Takeover and Persistent Mailbox Access

Compromising a genuine mailbox gives attackers something spoofing cannot: access to a trusted identity.

Once inside an account, an attacker may search conversations, invoices, customer information, password-reset messages, and payment discussions. They may also wait for an opportunity to insert fraudulent instructions into a legitimate transaction.

How Attackers Gain Access

Mailbox compromise can begin with credential phishing, password reuse, malware, stolen browser sessions, token theft, weak account recovery, or abuse of older authentication methods.

Multifactor authentication reduces many password-based attacks, but implementation matters. Weak recovery procedures, legacy protocols, session theft, and malicious application permissions can still provide a route into the account.

An assessment should therefore look beyond whether administrators have simply enabled MFA.

How Attackers Maintain Access

After compromising a mailbox, attackers may create forwarding rules, hide messages, delete warnings, add delegated access, grant permissions to malicious applications, or keep existing sessions active.

This is why a password reset alone may not fully contain a compromised account.

Administrators should also review active sessions, forwarding settings, inbox rules, delegated access, and connected applications.

Endpoint security matters as well. A mailbox can still be exposed if browser sessions, authentication tokens, or saved credentials are stolen from a compromised workstation. Where this occurs, findings should connect with workstation-focused security testing.

Business Email Compromise Requires Process Controls

Business email compromise often targets financial and operational decisions rather than malware. Attackers may focus on supplier payments, payroll, bank-detail changes, procurement, legal documents, executive requests, or sensitive customer information. Technical controls can reduce the likelihood of compromise, but they cannot determine whether a payment request is commercially legitimate.

Businesses therefore need independent verification for high-risk instructions. A request to change supplier bank details, approve an unusual transfer, release sensitive information, or bypass a normal approval process should be confirmed through a trusted channel that does not depend on the same email conversation.

For example, employees can verify payment changes using an established phone number rather than contact information included in the requesting email. These procedures must also be practical. If employees regularly bypass them because they are too complicated, they provide little protection.

Detection and Response After a Suspicious Email

Prevention will not block every malicious email.

Organisations also need the ability to investigate suspicious messages and contain compromised accounts quickly.

Users should have a simple way to report suspicious email. Security teams should then be able to examine sender information, message headers, authentication results, URLs, attachments, recipients, sign-in activity, forwarding rules, and related mailbox changes.

Where account compromise is suspected, the response may require more than changing the password.

Administrators may need to revoke active sessions, remove malicious rules, disable unauthorised forwarding, review delegated access, withdraw application permissions, and search for similar messages across other mailboxes.

Logging is important during this process. If sign-in or mailbox activity is not retained long enough, investigators may be unable to determine what the attacker viewed or changed.

The organisation should also consider external impact. Customers or suppliers may need to be warned if a trusted mailbox has been used to send fraudulent messages.

When Businesses Should Prioritise Email Security Testing

Email security testing is especially useful after changes to the organisation’s email environment.

This may include launching a new domain, migrating to another email provider, adopting Microsoft 365 or another cloud platform, introducing new third-party email services, or expanding remote working.

Testing should also be considered after suspicious sign-ins, mailbox compromise, repeated phishing campaigns, payment fraud, executive impersonation, or the discovery of unauthorised forwarding rules.

Higher-risk accounts may deserve additional attention. Finance, payroll, executives, IT administrators, procurement teams, legal staff, and customer-facing employees can be particularly attractive targets because they often have access to sensitive information or important business processes.

A risk-based assessment can therefore focus more heavily on privileged users, shared mailboxes, externally visible staff, and accounts involved in financial decisions.

Final Thoughts: Protect the Trust Attached to Every Message

Email security is not only about stopping spam.

It protects the trust employees, customers, suppliers, and business partners place in messages that appear to come from legitimate people and organisations.

Weak domain authentication can support impersonation. Poor mailbox security can turn one compromised account into long-term access. Weak verification processes can turn a convincing email into financial loss even when no malware is involved.

An email security assessment helps organisations understand how these weaknesses interact and whether attackers could imitate the business, compromise accounts, maintain access, bypass filtering, or exploit trusted business processes.

Aegixis VAPT Services can assess email domains, Microsoft 365 and other cloud email environments, mailbox security, authentication controls, filtering, impersonation protection, audit logging, and controlled phishing scenarios.

By combining technical validation with realistic business context, Aegixis helps organisations reduce phishing, spoofing, account takeover, and business email compromise risk without relying on a single security control or training exercise.