Summary
An unrecognized subdomain in Sender Score typically indicates that the return-path domain (5321.MailFrom), responsible for handling bounces, differs from the sending domain (5322.From). This is standard practice for bounce management and spoofing prevention. Possible causes include ESP configurations, authentication misalignments (SPF, DKIM, DMARC), third-party integrations, or recent email campaign changes. While Sender Score itself might be a vanity metric, investigating authentication settings and ESP configurations is crucial. Contacting deliverability experts and focusing on engaged addresses is advised if delivery issues persist.
Key findings
- Return-Path vs. Sending Domain: The unrecognized subdomain is likely the return-path domain (5321.MailFrom) used for managing bounces, which is different from the sending domain (5322.From).
- ESP Configurations: ESPs often automatically configure subdomains for bounce processing, tracking, and reputation management.
- Authentication Issues: Misconfigured SPF, DKIM, and DMARC records can cause discrepancies, leading to unfamiliar subdomains in Sender Score.
- Third-Party Integrations: The subdomain might be related to a third-party vendor or specific tracking mechanisms.
- Sender Score Validity: Sender Score may not always accurately reflect deliverability; focus on actual delivery rates and engagement metrics.
Key considerations
- Check Email Headers: Examine email headers to identify the return-path domain and confirm it aligns with your email infrastructure.
- Verify Authentication: Ensure your SPF, DKIM, and DMARC records include all sending sources, including ESP-managed subdomains.
- Consult Your ESP: Contact your ESP to understand the purpose of the subdomain and ensure proper configuration.
- Review Integrations: Examine third-party integrations to identify any unfamiliar domains and their impact on your sending reputation.
- Monitor Alignment: Ensure your DMARC policies and SPF/DKIM records are aligned correctly to avoid deliverability issues.
- Engage Experts: If delivery problems persist, seek advice from deliverability experts or contact relevant support teams (e.g., Proofpoint, SFMC).
- Engage Your Audience: Prioritize mailing to engaged addresses to improve sender reputation and overall deliverability.
What email marketers say
12 marketer opinions
Unrecognized subdomains in Sender Score often stem from configurations related to bounce handling, sender authentication (SPF, DKIM, DMARC), or third-party ESP setups. The return-path domain, which manages bounces, is frequently different from the sending domain. Investigations should include checking email headers, authentication records, ESP configurations, and recent email campaign changes.
Key opinions
- Return-Path Domain: Sender Score might be showing the return-path domain, used for handling bounces, which is often different from the sending domain.
- ESP Configuration: Subdomains are often automatically configured by ESPs for bounce processing, tracking, or reputation management.
- Authentication Issues: Improperly configured SPF, DKIM, and DMARC records can cause discrepancies, leading to unfamiliar subdomains in Sender Score.
- Third-Party Vendors: The subdomain might be associated with a third-party vendor used for specific tracking or other purposes.
Key considerations
- Check Email Headers: Examine email headers to identify the return-path domain and confirm it aligns with your sending infrastructure.
- Review Authentication Records: Ensure your SPF, DKIM, and DMARC records accurately reflect all sending sources, including subdomains used by your ESP.
- Contact ESP: Consult with your ESP to understand the purpose of the unrecognized subdomain and ensure proper configuration.
- Verify Integrations: Review all third-party integrations to identify any unfamiliar domains and their impact on your email sending.
- Monitor DMARC Alignment: Pay attention to your DMARC reports. Domain alignment ensures the return-path and from domains match, or are at least related.
Marketer view
Email marketer from Quora suggests that if you are using an Email Service Provider (ESP) like SendGrid or Mailgun, it's likely the subdomain is part of their infrastructure for managing bounces and feedback loops. Consult your ESP's documentation or support for details.
21 Nov 2024 - Quora
Marketer view
Email marketer from Email Geeks shares that senderscore is likely picking up your return-path domain. You can confirm this by checking the source code of your emails and looking at the headers.
6 Jul 2024 - Email Geeks
What the experts say
5 expert opinions
An unrecognized subdomain in Sender Score is often the return path or bounce domain (5321.MailFrom), which is used for handling bounces and protecting sender reputation. This domain is typically different from the domain displayed to the user (5322.From). While Sender Score might be a vanity metric, ensuring proper configuration is essential. If delivery issues persist, contacting deliverability experts and focusing on engaged addresses is recommended.
Key opinions
- Return-Path Domain: The unfamiliar subdomain is likely the return path/bounce domain (5321.MailFrom), used for handling bounced messages.
- Domain Differentiation: The return-path domain (5321.MailFrom) is often different from the domain displayed to recipients (5322.From).
- Sender Score Perspective: Sender Score might be a vanity metric, and if emails are delivering well, the subdomain issue may not require immediate action.
Key considerations
- Identify Return-Path: Confirm if the unfamiliar subdomain is indeed the return path/bounce domain by examining email headers.
- Assess Deliverability: Evaluate if there are actual deliverability issues. If emails are delivering well, the subdomain discrepancy might be less critical.
- Seek Expert Advice: If delivery problems persist, contact deliverability experts, such as those at Proofpoint or SFMC, for assistance.
- Focus on Engagement: Prioritize mailing to engaged addresses to improve sender reputation and overall deliverability.
Expert view
Expert from Email Geeks explains that based on the name 'bounce', it is probably the return path / bounce domain for some part of your mail stream.
7 Jul 2023 - Email Geeks
Expert view
Expert from Word to the Wise explains that different domains are used for different purposes. The domain used in the 5321.MailFrom (Return-Path) is often different from the domain in the 5322.From (the address displayed to the user). This is a common practice for handling bounces and protecting sender reputation. An unfamiliar subdomain could be the Return-Path domain used by your ESP.
6 Aug 2023 - Word to the Wise
What the documentation says
5 technical articles
Unrecognized subdomains in Sender Score often appear because the return-path (5321.MailFrom) domain, used for bounces and feedback loops, differs from the sending (5322.From) domain. This is a standard practice. However, issues can arise from misaligned SPF and DKIM records or strict DMARC policies. Ensuring all sending sources, including ESP-managed bounce subdomains, are correctly authenticated in SPF records is critical.
Key findings
- Return-Path Differentiation: The return-path (5321.MailFrom) domain is intentionally different from the sending (5322.From) domain for bounce handling and spoofing prevention.
- Authentication Alignment: Variations in SPF and DKIM alignment across domains can lead to unexpected subdomains appearing in Sender Score.
- DMARC Impact: Strict DMARC policies can cause issues if sending and return-path domains are not properly aligned.
- SPF Configuration: Incorrect SPF configuration, particularly the failure to include ESP-managed bounce subdomains, can lead to Sender Score flagging the subdomain.
Key considerations
- Verify Authentication Records: Confirm that SPF, DKIM, and DMARC records are correctly configured and aligned across all sending domains.
- Review ESP Settings: Ensure that the ESP's bounce subdomain is included in your SPF record.
- Evaluate DMARC Policies: Assess whether DMARC policies are overly strict and causing issues due to domain misalignment.
- Monitor Sender Score: Regularly monitor Sender Score to identify and address any discrepancies in domain configuration.
Technical article
Documentation from SparkPost states that unexpected subdomains can appear due to variations in SPF and DKIM alignment. If your authentication isn't correctly aligned across all sending domains, it can lead to confusion in Sender Score.
14 Jan 2025 - SparkPost Documentation
Technical article
Documentation from Validity Support explains that the return-path domain is often different from the sending domain and is used for handling bounces and feedback loops. The subdomain might be a designated bounce domain used by your email service provider or marketing automation platform.
4 Apr 2022 - Validity Support
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