What Is Misdirected Email and Why Does It Matter?

The smallest address-bar mistake can become the biggest data breach.

Misdirected email is one of the most common - and most avoidable - causes of data exposure.

From choosing the wrong “Sam” via autocomplete to CC’ing a whole list instead of BCC, a split-second slip can reveal sensitive information to people who should never see it.

And while attacks dominate headlines, day-to-day human error continues to drive a huge share of reportable incidents across sectors.

Let’s look at misdirected email, why it matters for people and organisations, and how to prevent it with controls that address the reality of human error - including when and why to use secure email tools.

• What Is Misdirected Email?
• Why Does It Matter?
• How Does It Happen?
• What Do Regulators Expect?
• How Do You Prevent It?
• What Should You Do After a Mistake?
• When to Use Secure Email

What Is Misdirected Email?

What Counts as “Misdirected Email”?

Misdirection includes sending to the wrong person, exposing recipients’ addresses by using CC instead of BCC, attaching the wrong file, or forwarding sensitive content to someone without a lawful need to see it.

Under the UK General Data Protection Regulation (UK GDPR), these events can constitute a personal data breach requiring assessment and, in some cases, reporting.

Is Misdirected Email Really That Common?

Regulatory trend data in the UK has, for years, placed “wrong recipient/email” among the most frequently reported categories.

Industry studies also report outbound email incidents as widespread, with misaddressing and incorrect attachments common among the triggers.

Why Does It Matter?

What Harms Can a Simple Addressing Error Cause?

Real-world cases include disclosures of health details, financial identifiers, and personal circumstances.

Even when data is not overtly “sensitive,” revealing identities or contact lists can cause distress, safety concerns, and reputational damage.

For organisations, the consequences include incident-handling costs, potential regulatory scrutiny, and erosion of customer trust.

Unlike other types of cyber breaches, most misdirection incidents aren’t caused by “bad actors” - they’re good people working at speed.

For this reason, misdirection should be treated as a design and control problem to be engineered out, not a blame exercise.

How Does It Happen?

What Are the Typical Root Causes?

Common patterns involved in misdirected email errors include:

• Autocomplete picking the wrong contact with a similar name.
• Legacy distribution lists that include unintended recipients.
• Near-identical filenames that lead to mis-attachments.
• Using CC for bulk, sensitive messages (instead of BCC).

UI conventions, time pressure, and complex identity relationships all contribute to making slips likely to happen.

Does Email “Recall” Fix the Problem?

“Email recall” features found in popular email clients often provide a false sense of security for users.

For example, Outlook’s recall feature works only within the same Microsoft 365/Exchange organisation and cannot retrieve messages sent externally.

Gmail or Apple Mail’s “Undo Send” function also leaves security gaps - though it delays dispatch for a short window, which helps with typos, it doesn’t cover mistakes discovered minutes or hours later.

Learn more about how to recall an email in Outlook.

What Do Regulators Expect?

Which Rules Apply When Email Goes Astray?

UK GDPR requires appropriate technical and organisational measures for email processing.

If a misdirection creates a likely risk to people’s rights and freedoms, organisations must report the breach to the regulator within the statutory window (often 72 hours after becoming aware of it) and, where required, notify affected individuals.

The regulator has also advised against using BCC for sensitive bulk messages - safer alternatives are expected.

What About Sector Expectations (Public Sector, Financial Services)?

Government email guidance emphasises encryption in transit and authenticated sending domains alongside strong operational controls.

In regulated industries, duties around consumer protection and robust systems require an even higher bar of proactive measures to prevent email leakage and contain impact quickly when it occurs.

This includes guidance from the Financial Conduct Authority, the Care Quality Commission, and the Solicitors Regulation Authority.

Email Compliance Snapshot: Who Expects What?

How Do You Prevent It?

Start with Layered Technical Controls for Email Risk Reduction

Protect the channel: Configure DMARC, SPF, and DKIM correctly to stop spoofing and strengthen trust signals.

Add intelligent DLP: Use rules or adaptive models to check recipients, keywords, and attachment contexts pre-send, with smart prompts for risky actions (e.g., sending an email to multiple people with a subject line containing the phrase “confidential”).

Use access-controlled delivery for sensitive content: Use secure email platforms that offer recipient authentication and the option to revoke access if a mistake occurs.

Strengthen the Human System with Simple Process Guardrails

• Minimise bulk, sensitive emailing where possible.
• For high-risk sends, require a second-pair-of-eyes, a pre-send checklist, or data loss prevention filters.
• Cleanse distribution lists and disable stale email groups.
• Conduct regular training to reinforce the importance of double-checking addresses and attachments, and use BCC appropriately.
• Reinforce training with technology by building prompts into workflows.

Does TLS Stop Misdirected Email? (No - and Here’s Why)

Most email providers use TLS (Transport Layer Security) to protect messages as they travel between servers.

However, this does nothing to stop a message going to the wrong person or a CC list being exposed.

To reduce harm from human error, you need identity checks and controls for messages and attachments, and the ability to revoke after sending.

What Should You Do After a Mistake?

First-Hour Priorities After a Misdirected Send

Move fast - if the email is internal, attempt a recall if possible.

If it’s an external message, contact the unintended recipient and request deletion without further dissemination. Restrict access to any linked files.

Record the details of the incident, review the potential impact on individuals, and prepare to inform those affected and the relevant regulator if there is a significant risk.

Inform internal stakeholders (IT, legal, comms) early to coordinate a consistent response.

What’s a Realistic “Unsend” Window? (Seconds, Not Hours)

Client-side delays (e.g., a short “Undo Send”) help catch immediate mistakes but won’t save you minutes later.

Build preventative checks and access-controlled delivery into the process so that, if misdirection happens, content can’t be opened in the first place - or can be revoked quickly.

Secure email platforms like Mailock are designed to add this layer of human authentication so only intended recipients can gain access to any sensitive email contents.

When to Use Secure Email

Reduce Misdirection Risk with Recipient Authentication and Revoke

Secure email platforms add recipient authentication (challenge Q&A, SMS, or federated identity) so the wrong person can’t open content even if addressed incorrectly.

With a robust revoke capability, access to secure messages and attachments can also be withdrawn after send.

Tracker audit trails and configurable security alerts also support compliance and continuous habit reinforcement.

Complementing Gateways, DLP, and TLS - Not Replacing Them

Keep your inbound email scanning, DMARC, and transport encryption - they address different threats.

Use outbound secure email solutions for sensitive communications where identity verification, least-privilege access, and post-send control close the human-error gap.

"If you design for people as they really work - busy, distracted, mobile - you accept that mistakes will happen.

The goal is to make those mistakes harmless."

Paul Holland, Founder, Beyond Encryption

FAQs

Is Misdirected Email the Same as a Cyber Attack?

No. Misdirection is usually accidental, not malicious.

But the impact on individuals can be just as serious, so prevention and rapid response are essential.

Should We Ever Use BCC for Sensitive Bulk Emails?

Where content is sensitive, prefer authenticated portals or secure links with access control.

The ICO has warned repeatedly that BCC is fragile and error-prone for high-risk communications.

What’s the Business Case to Invest Here?

Outbound email incidents are frequent, remediation is costly, and a small cohort of senders typically drives a disproportionate share of risky events.

Targeted prompts, identity checks, and post-send control reduce likelihood and impact, protecting customer/recipient trust.

References

Data Security Incident Trends, Information Commissioner’s Office (ICO), 2025

Personal Data Breaches: A Guide, ICO, 2025

Guidance: Sending Bulk Communications by Email, ICO, 2023

Reprimand: The Patient and Client Council, ICO, 2023

Reprimand: South Tees Hospitals NHS Foundation Trust, ICO, 2024

Email Security and Anti-Spoofing Collection, National Cyber Security Centre (NCSC), 2025

Securing Government Email, UK Government, current guidance page

Recall an Outlook Email Message, Microsoft Support, 2025

Send or Unsend Gmail Messages, Google Support, 2025

Data Loss Landscape Report, Proofpoint, 2024

Email Security Risk Report: Key Stats, Egress, 2024

Reviewed by

Sam Kendall, 25.09.25