Why do Salesforce Marketing Cloud hard bounces show a different recipient email address while engagement continues?
Matthew Whittaker
Co-founder & CTO, Suped
Published 18 Apr 2025
Updated 19 Aug 2025
9 min read
It can be perplexing to see hard bounces in Salesforce Marketing Cloud (SFMC) showing a recipient email address different from the one you sent to, especially when your data indicates continued engagement like opens and clicks. This scenario often leaves email marketers scratching their heads, wondering how an email could bounce as undeliverable while simultaneously showing signs of being read.
This paradoxical behavior is not as uncommon as it might seem and usually points to specific technical intricacies in email delivery and how bounce messages are handled. It's often related to email forwarding, where a message is sent to one address but then forwarded to another, or to automated security scans that mimic user engagement. Understanding these underlying mechanisms is key to interpreting your bounce data accurately and maintaining a healthy sender reputation.
While it can be tempting to dismiss these bounces due to apparent engagement, ignoring hard bounce notifications can harm your deliverability over time. Even if some engagement is happening, a persistent hard bounce indicates that the primary recipient address is ultimately invalid or inaccessible. This article will delve into the technical reasons behind these confusing bounce reports and provide clarity on how to manage them effectively within Salesforce Marketing Cloud.
The mechanics of email forwarding and asynchronous bounces
One of the most common explanations for a hard bounce showing a different recipient address is email forwarding. When an email is sent from SFMC to an initial recipient, let's say hello@example.com, that recipient's mail server might have a forwarding rule in place. This rule automatically sends the email to another address, such as someoneelse@differentdomain.com. If the forwarded address is invalid or non-existent, the bounce message originates from the final mail server attempting delivery to that secondary address, not the initial one. This is often referred to as a remote or asynchronous bounce.
The reason SFMC receives this bounce, even though it wasn't the direct recipient of the failed delivery, lies in the Variable Envelope Return Path (VERP) encoding. SFMC uses VERP to append unique identifiers to the return path (also known as the bounce address or Mail From address) for each email sent. This allows it to precisely match bounce messages back to the original subscriber and campaign, regardless of where in the forwarding chain the bounce occurs. When a message is forwarded naively (without altering the return path), any subsequent delivery failure at the final destination will send the bounce notification back to SFMC's designated bounce handler.
Mailbox providers typically send two types of bounces, synchronous (immediate) and asynchronous (delayed). Asynchronous bounces are common in these forwarding scenarios. The initial mail server accepts the email, thinking it can deliver it, but then, after the forwarding, the ultimate destination (the generic Danish MBP in our example) determines the address is unknown and sends a bounce back to the original sender's return path. This process can cause the delay and the discrepancy in the reported recipient.
It's important to understand that the initial mail server (the Danish doctors domain) would not typically generate a bounce in this situation, as it successfully accepted the email for forwarding. The bounce comes directly from the final recipient's mail server. This is why the middleman (the forwarding server) isn't necessarily aware of the ultimate bounce, and SFMC is able to catch it.
Understanding engagement versus bounces
The continued engagement (opens and clicks) from the same subscriber key, despite the hard bounces, adds another layer of complexity. There are a few possible explanations for this seemingly contradictory behavior.
Spam filter pre-fetching or scanning
Many modern spam filters, particularly those employed by large mailbox providers or corporate security solutions, will pre-fetch or scan emails upon arrival. This involves opening the email and clicking on links to analyze content and identify malicious activity before it reaches the recipient's inbox. These automated actions are often recorded as opens and clicks in your SFMC tracking data, even if the email ultimately hard bounces or is never seen by a human. This is a common reason emails can bounce after appearing to be opened.
Multiple forwarding destinations or access points
It's also possible that the original email address, hello@example.com, is configured to forward emails to multiple secondary addresses. If one of these forwarded addresses is invalid and triggers a hard bounce, other forwarded copies of the email might still be successfully delivered and engaged with. Additionally, the original inbox for hello@example.com might still be accessible via webmail or another email client, allowing the subscriber to continue viewing and interacting with messages, even if one of its forwarding paths has failed.
Real user engagement
Direct interaction: The subscriber opens emails in their primary inbox or via a working forwarding address.
Intentional clicks: Links are clicked by the actual user, leading to website visits or conversions.
Consistent behavior: Engagement patterns align with typical user behavior and are not isolated incidents.
Automated activity (spam filters)
Pre-delivery scanning: Automated systems open emails and click links to check for malicious content before delivery.
Irregular patterns: Opens and clicks might occur immediately after sending, often from generic IP addresses.
Discrepancy: Engagement data appears for addresses that are also hard bouncing or show no other signs of life.
Distinguishing between real engagement and automated activity is crucial for accurate list hygiene. While Salesforce Marketing Cloud provides comprehensive tracking, sometimes deeper analysis of IP addresses, user agents, and timing of engagement events is required to make a definitive judgment.
Salesforce Marketing Cloud's bounce handling
Salesforce Marketing Cloud has sophisticated mechanisms to handle email bounces and manage subscriber status. When a hard bounce occurs, SFMC typically flags the subscriber as undeliverable and prevents future sends to that address. This is a critical feature for maintaining your sender reputation and avoiding email blocklists (or blacklists).
The platform distinguishes between various bounce categories and reasons, such as user unknown, mailbox full, or content related issues. A hard bounce, specifically a 5.1.1 Recipient address rejected: User unknown bounce, signals a permanent delivery failure. SFMC's automation is designed to handle this by suppressing the problematic address automatically, regardless of any perceived engagement. This is critical for good email deliverability.
Another aspect to consider is the use of BCC (Blind Carbon Copy) functionality within SFMC. While less common, if BCC recipients are configured, a bounce from a BCC'd address could also appear in your reports. However, as noted in the scenario, this typically results in a recognizable email address in the bounce message and tends to happen more broadly across sends, rather than isolated to a single subscriber key with an unfamiliar bounce address.
It's important to differentiate between actual hard bounces and other types of delivery issues. SFMC's robust bounce management ensures that addresses that consistently hard bounce are suppressed, which helps prevent future attempts to send to non-existent mailboxes. For more details on this, see how Salesforce Marketing Cloud handles email bounces.
Actionable steps and data interpretation
When faced with such puzzling hard bounce reports, the best course of action is generally to trust the bounce data provided by Salesforce Marketing Cloud. While it's tempting to investigate every anomaly, the automated bounce management processes in SFMC are designed to protect your sender reputation and optimize deliverability.
Recommended actions
Trust the hard bounce: Allow SFMC's automated bounce management to suppress the hard-bounced email address.
Prioritize deliverability: Removing non-existent addresses from your list is crucial for long-term email health.
Avoid over-investigation: Unless a significant pattern of unusual bounces emerges, deep dives into individual anomalies are often unnecessary.
Review data periodically: Regularly monitor your bounce rates and manage hard bounces for unusual trends.
While it can feel counterintuitive to remove a subscriber who appears to be engaging, the hard bounce is a clear signal from the receiving mail server that the primary delivery path has failed permanently. Continued attempts to send to such addresses will only increase your bounce rate, potentially leading to your IP or domain being put on a blocklist (or blacklist)and impacting your overall email deliverability for all your legitimate recipients.
Focusing on maintaining a clean and engaged list, rather than trying to salvage every single address, is the most effective strategy for long-term email marketing success. SFMC's built-in bounce management is designed to assist with this, so leverage its capabilities.
Views from the trenches
Best practices
Actively use Salesforce Marketing Cloud’s bounce management automation to suppress hard-bounced addresses automatically.
Regularly review your email list to identify and remove disengaged subscribers, especially those with consistent bounces.
Monitor email metrics beyond opens and clicks to understand true engagement, considering deliverability status.
Common pitfalls
Over-analyzing every bounce message for unique scenarios, which can detract from overall list hygiene efforts.
Ignoring hard bounces due to perceived engagement, risking damage to sender reputation and future inbox placement.
Not understanding the difference between synchronous and asynchronous bounces, leading to misinterpretation of data.
Expert tips
The VERP-encoded return path in SFMC allows for precise tracking of bounces, even from forwarded emails.
Spam filters often pre-fetch emails, generating opens and clicks before the email reaches a recipient, which can explain the discrepancy.
If a forwarded email's final destination is invalid, the bounce goes directly back to the original sender if the return path is preserved.
Expert view
Expert from Email Geeks says that asynchronous bounces can certainly occur for email forwarding scenarios, and seeing the full rejection message or knowing the involved domains might provide more clues.
2024-07-03 - Email Geeks
Expert view
Expert from Email Geeks explains that when mail is forwarded naively, the return-path remains unchanged. If the final recipient domain cannot deliver the email, it sends an asynchronous bounce directly to the address in the return-path, allowing SFMC to match it with the original subscriber via VERP.
2024-07-03 - Email Geeks
Key takeaways for managing SFMC bounces
The phenomenon of Salesforce Marketing Cloud hard bounces displaying different recipient email addresses while engagement seems to continue is primarily a result of email forwarding complexities and the behavior of automated spam filters. The VERP encoding used by SFMC is effective at capturing these asynchronous bounce messages, even when they originate from a secondary, forwarded address.
While the presence of opens and clicks might suggest continued engagement, it is often automated security scanning or the subscriber accessing the email through an alternative, working channel. The hard bounce, especially a user unknown message, is a definitive signal that the email could not be delivered to its ultimate destination. Trusting SFMC's bounce management system to suppress these addresses is crucial for maintaining a clean list and a strong sender reputation.
Prioritize list hygiene by adhering to hard bounce suppression, even if initial tracking data seems contradictory. This approach ensures your marketing efforts reach valid inboxes and safeguards your email program's long-term health.
