Why would a customer receive an email intended for another customer with the wrong email in the TO field?

Key findings

• Recipient vs. header: The email address specified in the SMTP RCPT TO command determines actual delivery, while the 'To' header field is merely a display element. These two do not always need to match for an email to be delivered.
• Sending system errors: Misconfigurations or bugs in the sending platform, email service provider, or custom messaging code can lead to incorrect 'To' headers being generated while the email is sent to the correct underlying address (or vice-versa).
• Data mismatches: Errors in customer databases or CRM systems, where recipient data for different customers might be incorrectly linked or merged, can cause this issue.
• Display name trickery: The 'To' field might display a different email address as the 'display name' while the actual email address used for delivery is the recipient's own address. For example, 'Customer B <customerA@example.com>'.
• Human error: In manual sending scenarios or data entry, a user might mistakenly enter the wrong recipient's email into the 'To' field or associate the wrong 'display name' with an email address. This is less common for automated bulk sends but still possible.
• Gmail's dot quirk: For Gmail accounts, periods in email addresses before the '@' symbol are ignored. So, john.doe@gmail.com is the same as johndoe@gmail.com. A sender might target one version while the recipient has the other, leading to confusion though the delivery is correct. This is specific to Gmail and might not apply to other providers like sbcglobal.

Key considerations

• Header analysis: Obtaining the full email headers from the affected recipient is the most critical step. Headers provide a detailed log of the email's journey and can reveal discrepancies between the 'To' field and the actual delivery address. Understanding these headers is part of a broader approach to improving email deliverability.
• System audit: Thoroughly review your email sending processes, from database integration to message composition and transmission, to identify any potential points of failure or data mismatch. Pay close attention to how personalization errors in email headers might occur.
• Database validation: Implement rigorous data validation and cleansing routines for your customer databases to prevent incorrect or duplicate entries. Ensuring data integrity is a fundamental step in preventing such email misdeliveries.
• Privacy implications: If sensitive information is included, receiving an email intended for someone else can constitute a data breach under regulations like GDPR. Organisations must understand the implications of wrong email address data breach claims and respond accordingly.

Key opinions

• Check database integrity: Many marketers suggest that a primary cause could be an issue with the contact database being mismatched or having incorrect entries for recipients.
• Sending software issues: Problems within the email sending software or service itself are often suspected, including bugs or misconfigurations that affect how recipient data is handled and displayed.
• Human data entry errors: Sometimes, the issue isn't technical but human, where sales representatives or data entry personnel might accidentally mix up customer details, leading to emails being sent to the wrong person despite appearing correct in the 'To' field.
• Display name vs. actual address: A common theory is that the 'To' field shows one email as a 'display name' while the actual delivery address is different, causing confusion for the recipient who sees the incorrect address.

Key considerations

• Verify CRM data: Before escalating to technical debugging, marketers should first confirm that the customer relationship management (CRM) system or database has the correct data input for the recipient in question.
• Examine email headers: Obtaining the full email headers is crucial for diagnosing routing issues. This provides insight into how the email was actually delivered versus how it was displayed. This is a vital part of running an email deliverability test.
• Review sending logic: Marketers should work with developers to review the logic behind their email sending or message composition code to identify any potential 'cockups' that could lead to such inconsistencies.
• Learn from similar experiences: Many users report receiving emails intended for others with similar or identical names, especially on platforms like Gmail (due to its dot-ignoring policy). These anecdotes highlight the importance of careful list management and avoiding relying solely on perceived uniqueness of email addresses. A resource like Ask Leo! offers insights into such common email quirks.

Key opinions

• Recipient field vs. delivery: Experts affirm that the email recipient an email is delivered to is technically unrelated to the address displayed in the 'To' field. Delivery is dictated by the SMTP envelope recipient, not the header.
• Sending infrastructure ‘cockups’: Misconfigurations or errors in the sender's own system or message composition code are frequently cited as the reason for such display discrepancies. This includes the logic that populates the 'To' header.
• Confirm display vs. actual: It's important to verify if the 'To' field is showing one email as the 'display name' while the actual email (used for routing) is the real recipient's address. This is a common way the issue can manifest visually.
• Beyond human error: While human error (e.g., mixing up customer names in a CRM) should be checked, technical experts lean towards systemic issues with the sending platform or database as the likely culprits.

Key considerations

• Retrieve full email headers: The single most crucial diagnostic step is to obtain the full email headers from the recipient who received the misaddressed email. This provides the authoritative record of the email's path and intended recipient. This is essential for proper troubleshooting of missing emails.
• Consult developers: Email experts often advise engaging with the smartest developers working on the sending system. Their insight into the code and database can quickly uncover logical errors that might cause the 'To' field discrepancy.
• Consider the sending platform: It's important to consider that the issue might originate from the email sending platform itself. This could involve an ESP's internal routing, or how they handle dynamic 'To' field population, affecting broader email deliverability.
• Investigate underlying data: Thoroughly check the CRM or database for correct data input for the specific recipient. Issues like duplicated entries or incorrect field mapping can lead to sending systems pulling the wrong 'To' header information. This also relates to how internal email addresses end up on lists.
• Distinguish from spoofing: While this issue is typically a sender-side misconfiguration, it's distinct from outright spoofing attempts where the sender's identity is faked, though both involve misleading 'From' or 'To' fields. Understanding forged headers is key.

Key findings

• SMTP envelope vs. message header: Email delivery is controlled by the 'envelope' information (specifically, the RCPT TO command during SMTP transmission), not the 'To:' field in the message header. The header is primarily for the recipient's email client display.
• RFC 5322 compliance: RFC 5322, which defines the format of internet text messages, specifies the 'To' field as a destination address for the message, but it doesn't dictate the actual delivery. Discrepancies between this and the envelope address are possible due to various sending configurations or errors.
• Data breach risk: Sending an email intended for one person to the wrong recipient, especially if it contains personal information, can constitute a data breach. This is a significant compliance and legal concern under privacy regulations like GDPR.

Key considerations

• Header review: When investigating such issues, documentation consistently advises reviewing the full email headers (raw message source) to understand the discrepancy between the 'To' header and the 'Delivered-To' or similar fields that indicate the actual recipient. This is fundamental for identifying spoofing attempts or misconfigurations.
• Compliance and mitigation: Organisations must implement measures to mitigate the risk of emails being sent to unintended recipients, especially when sensitive information is involved. This includes robust data validation, secure email sending practices, and clear incident response plans in case of a breach.
• Understanding email standards: A deeper understanding of email standards, such as those defined by the Internet Engineering Task Force (IETF), can help troubleshoot discrepancies between displayed headers and actual routing. This technical knowledge is crucial for advanced deliverability issues.