Why would a customer receive an email intended for another customer with the wrong email in the TO field?
Matthew Whittaker
Co-founder & CTO, Suped
Published 17 Jun 2025
Updated 19 Aug 2025
8 min read
It can be quite bewildering to receive an email that, at first glance, appears to be meant for someone else, especially when their email address is clearly displayed in the "To" field. You might find yourself wondering if there's been a mix-up with your email provider, a data breach, or some inexplicable technical glitch. This scenario, while confusing, is something I've seen play out in various forms within the email ecosystem.
The immediate reaction is often concern, not just for privacy but also for the integrity of email delivery systems. Understanding why this happens requires a look beyond the surface level of what an email client displays, delving into how email routing actually works. It's a complex interplay of human actions, database configurations, and mail server protocols that can lead to such unexpected deliveries.
Understanding the delivery chain
One of the most common culprits behind an email landing in the wrong inbox, despite an incorrect "To" field, is simple human error. This isn't always about a sender typing the wrong address, though that does happen. Sometimes, it's a mix-up in a company's customer database where customer A's email might be incorrectly associated with customer B's details, or vice versa. When an email campaign or transactional message is sent, the system pulls what it believes to be the correct recipient, but the data itself is flawed.
Another scenario involves aliases or forwarding rules configured on the recipient's end. For instance, customer B might have set up an email alias or forwarding rule that redirects all mail intended for their address to customer A's inbox. In this case, the email is indeed addressed correctly to customer B but is then rerouted before it ever reaches their primary inbox. While less common, it is a possibility, especially within organizations where employees might set up internal forwarding for various reasons. You might find more details on what to do if you get emails for the wrong person from articles like this one by Wired.
Finally, while it's less frequent for the "To" field itself to be wrong in a legitimately delivered email, sometimes the issue stems from an email client's display logic. Some clients might attempt to resolve or display recipient names or addresses in a way that creates confusion, especially if there are multiple contacts with similar names or if the email was Blind Carbon Copied (Bcc) to you while showing another recipient in the To field. This is why checking the full email headers is crucial.
Technical causes and how they manifest
The distinction between the "To" header you see in your email client and the actual envelope recipient, which guides mail delivery, is key. Email servers route messages based on the envelope recipient, similar to how postal services deliver letters based on the address written on the envelope, not just the address inside the letter. If the envelope recipient is correct (your email address), but the "To" header is incorrect (customer B's email), the email will still land in your inbox. This often points to an issue with the sending system's message composition, where the content of the email, including header fields, is populated with incorrect data.
Misconfigurations in sending software or services are surprisingly common. Sometimes, a bug in an email sending platform or a custom script can cause the To field to be incorrectly populated even if the actual routing address (the envelope recipient) is correct. This is less about deliverability to the inbox and more about the internal data handling of the sending application. For example, a campaign might pull the wrong customer ID and thus the wrong "To" address for the displayed header, while sending to the correct, programmed recipient.
The scenario where the display name and actual email address in the "To" field are mismatched can also cause confusion. An email might technically be sent to customerA@example.com but the To: header displays "Customer B" <customerA@example.com>. In this case, the email is indeed going to the right place, but the displayed information is misleading. This can be a sign of poor data hygiene or a coding error during the email's generation.
Understanding these technical nuances is crucial for diagnosing delivery problems, as simply looking at the "To" field in a mail client doesn't tell the whole story. To fully comprehend why your emails might be failing, a deeper dive into the technical headers is often necessary.
Troubleshooting and analysis
Investigating a misdirected email
Obtain full headers: Ask the customer who received the email to provide the full email headers. This raw data contains the actual routing information, including the envelope recipient (`Delivered-To` or `X-Original-To` fields) and the path the email took.
Check sending logs: Cross-reference the email with your own sending platform's logs. These logs will show the exact recipient address your system attempted to send to. If your logs show customerA@example.com but the email header displays customerB@example.com, it points to a display issue or a processing error within your application, not necessarily a routing failure.
Review data sources: Investigate your customer relationship management (CRM) system or database. Look for any instances where customer A and customer B's data might have been merged, swapped, or incorrectly updated. This could explain why the wrong information appears in the email body or headers.
Once you have the full email headers, you can begin to piece together the puzzle. Focus on the `Received` headers, which show each server the email passed through, and the `Delivered-To` or `X-Original-To` headers, which explicitly state the final intended recipient at that specific mail server. These fields are far more reliable than the user-facing `To` header for understanding actual delivery paths. If you need help with this, you can use an email deliverability test.
If the headers confirm that the email was indeed routed to customer A's address, despite customer B's address being in the "To" field, the problem likely lies within your sending infrastructure, either at the application level or with your email service provider. This is a "cock-up" in your sending or message composition code, as one expert noted. It means the system correctly identified customer A as the recipient for sending but incorrectly populated the visible "To" field with customer B's details. Addressing these internal issues is critical for maintaining email deliverability and customer trust.
Preventing future occurrences
Preventing such issues from recurring involves a multi-faceted approach, starting with robust data validation and hygiene practices. Regularly auditing your customer databases for accuracy and consistency can catch mismatched records before they lead to misdirected emails. Implementing double opt-in processes for new sign-ups also reduces the chance of typos or incorrect email entries leading to future problems.
From a technical standpoint, thorough testing of your email sending workflows is essential. This includes testing how recipient data is pulled from your database, how it populates email templates, and how it is passed to your email service provider. Automated testing can help identify bugs that cause the "To" field to display incorrectly or that lead to incorrect envelope recipients. Reviewing your email authentication records, such as DMARC, SPF, and DKIM, ensures that your emails are properly authenticated, reducing the likelihood of them being flagged or misrouted by receiving servers due to authenticity concerns.
Finally, maintaining open communication with your customers is paramount. If a customer reports receiving an email not intended for them, take it seriously. Requesting the full email headers is a legitimate troubleshooting step that can provide invaluable insights into the delivery path and potential anomalies. This proactive approach not only helps resolve immediate issues but also strengthens customer trust and confidence in your email communications.
Views from the trenches
Best practices
Always validate email addresses at the point of entry to catch typos and prevent incorrect data from entering your system.
Regularly audit your customer database to ensure email addresses are accurate and linked to the correct customer profiles.
Implement robust error logging and monitoring for your email sending processes to quickly identify and address anomalies.
Common pitfalls
Overlooking discrepancies between the visible 'To' header and the actual envelope recipient, leading to misdiagnosed issues.
Assuming email delivery issues are always external (ISP, recipient server) without first checking internal data or sending logic.
Failing to review full email headers, which contain critical routing information for diagnosing complex delivery problems.
Expert tips
Use a canonical email format for all addresses in your database to standardize entries and minimize variations.
Leverage DMARC reports to detect potential spoofing attempts or misconfigurations that might lead to unusual email routing.
Set up internal alerts for any sudden spikes in bounce rates or customer complaints about misdirected emails.
Expert view
Expert from Email Geeks says the recipient an email is delivered to is unrelated to the address in the To: field.
2020-03-27 - Email Geeks
Expert view
Expert from Email Geeks says to check if the TO field is showing one email as the display name, but the actual email is the real recipient.
2020-03-27 - Email Geeks
Summary
Receiving an email intended for another customer, with their email in the "To" field, is a puzzling but solvable problem. It typically stems from a combination of human error, data inaccuracies, or technical misconfigurations within the sending system. The key to diagnosing and resolving these issues lies in understanding the difference between the visible "To" header and the actual envelope recipient, coupled with a thorough investigation of email headers and internal data.
By adopting stringent data hygiene practices, conducting comprehensive testing of email workflows, and leveraging detailed email headers for analysis, you can minimize the occurrence of such incidents. This approach not only ensures that your emails reach the correct recipients but also fortifies your brand's reputation and customer trust, essential components of effective email deliverability.
