What Is Email Security? Definition, Threats and Best Practices

Email security is the combination of technologies, policies and practices that protects email accounts, messages, users and data from unauthorized access, abuse and cyber threats. Effective email security works before, during and after delivery to stop malicious messages, protect sensitive information and help people respond safely.

Proofpoint observed a 94% year-over-year increase in global email threats, from 2.8 billion to 5.4 billion. That growth reflects more than higher volume. Threat actors now use automation and generative AI to create convincing lures, vary their techniques and exploit trusted relationships at scale.

Email security protects the confidentiality, integrity and availability of email. It helps ensure that only authorized people can access messages, that content is not altered without detection and that email remains available for legitimate business use.

The term covers a broad security discipline. It includes controls for inbound and internal threats, account compromise, outbound data loss and human behavior. It also includes processes for investigating suspicious messages and removing threats that are discovered after delivery. A message may pass sender-authentication checks and still be malicious if it comes from a compromised supplier account. Effective email security evaluates message content, intent, behavior and relationships in addition to authentication signals.

Modern email security uses overlapping controls because no single filter can identify every threat.

1.  Authenticate senders. SPF, DKIM and DMARC help receiving systems verify whether messages are authorized for a domain and reduce some forms of spoofing. Authentication does not prove that a message is harmless, especially when a legitimate account is compromised.

2.  Analyze messages and behavior. Security systems inspect sender reputation, language, intent, relationships, links, files, images and other signals to identify known and novel threats.

3.  Protect throughout the message lifecycle. Controls can act before delivery, inside the mailbox, when a user clicks and after delivery if new intelligence changes the verdict.

4.  Protect accounts and data. Multifactor authentication, identity monitoring, least-privilege access, encryption and data loss prevention reduce the impact of stolen credentials and risky data movement.

5.  Support people and response teams. Clear warnings, relevant training, one-click reporting and automated investigation help users and security teams contain threats faster.

Organizations focused on advanced inbound and internal email threats can evaluate Proofpoint Core Email Protection. Organizations that also need to address compromised accounts, suppliers, messaging and cloud collaboration can explore Proofpoint Collaboration Security Prime.

• Phishing and spear phishing. Phishing attacks impersonate a trusted person or organization to steal credentials, deliver malware or persuade a recipient to act. Spear phishing targets a specific person or role with a tailored message.
• Business email compromise and impersonation. Business email compromise messages use social engineering to request payments, change bank details or obtain sensitive information. The message may come from a spoofed address or a compromised legitimate account and may contain no malicious link or attachment.
• Account takeover and lateral phishing. After gaining access to an account, an attacker can send messages from a trusted identity, change mailbox rules, steal data or target colleagues and partners.
• Malicious links, attachments and QR codes. A message can lead to a credential-harvesting page or deliver malware and ransomware. QR codes and image-based lures can hide destinations from basic text scanning.
• Email bombing and legitimate-service abuse. Attackers can flood an inbox with subscription messages to distract a user or security team while another fraudulent action occurs.
• Outbound data loss. Sensitive data can leave through a misdirected message, the wrong attachment, deliberate exfiltration or a compromised account.

Email is central to business communication and gives attackers direct access to people, trusted relationships and valuable data. A single successful attack can lead to credential theft, fraudulent payments, malware infection, data loss or a broader compromise of cloud accounts and collaboration systems.

Email security reduces that risk by stopping threats earlier and limiting their impact. It can also help security teams investigate incidents faster, protect high-risk users and maintain controls over sensitive information moving through email.

1. Use SPF, DKIM and DMARC, and monitor their alignment and enforcement.
2. Require phishing-resistant multifactor authentication where possible and monitor for risky sign-ins, mailbox-rule changes and suspicious account behavior.
3. Add layered detection for phishing, BEC, malicious URLs, attachments, QR codes and messages from compromised trusted accounts.
4. Maintain pre-delivery, click-time and post-delivery controls so a message can be rechecked and removed when risk changes.
5. Apply data protection to outbound email, including misdirected messages, incorrect attachments and intentional exfiltration.
6. Make suspicious-message reporting easy, train people with relevant examples and use reported messages to improve detection and response.
7. Test controls regularly with simulations, configuration reviews and incident exercises. Track successful attacks, false positives, response time and user reporting rather than relying on blocked-message counts alone.

Email security works best as a layered program that protects messages, accounts, data and people throughout the email lifecycle. Review Proofpoint Core Email Protection for advanced email-focused defenses, or Proofpoint Collaboration Security Prime when threats extend into accounts, suppliers, messaging and cloud collaboration.