Why are mailto: unsubscribe emails from Laposte.net failing DMARC authentication?
Michael Ko
Co-founder & CEO, Suped
Published 30 Jul 2025
Updated 14 Aug 2025
6 min read
Summary
Emails sent via the mailto:unsubscribe mechanism from Laposte.net are encountering DMARC authentication failures. This issue primarily stems from a misconfiguration involving an intermediary service, Vade, which handles these unsubscribe requests. The problem arises because Vade's sending IP address is not authorized in Laposte.net's SPF record, and there appears to be no valid DKIM signature that aligns with the From domain. Given Laposte.net's DMARC policy is set to p=quarantine, these authentication failures lead to the emails being junked or rejected, causing significant compliance and deliverability challenges for recipients who are legally required to honor unsubscribe requests. Understanding how DMARC works is crucial for resolving such complex authentication issues, particularly when third-party services are involved in the email flow. For more details on DMARC authentication, consider reviewing a simple guide to DMARC, SPF, and DKIM.
Key findings
SPF misalignment: The IP address 185.187.30.19 used by Vade for sending mailto:unsubscribe emails is not included in Laposte.net's SPF record, leading to authentication failures.
DMARC policy impact: Laposte.net has a DMARC policy of p=quarantine, causing emails that fail DMARC to be quarantined or marked as spam.
Third-party sending: The emails are sent via vaderetro-safeunsubscribe.com, which seems to lack proper SPF or DKIM configuration for the Return-Path domain, leading to DMARC failure because the From domain (Laposte.net) is not aligned.
Impact on compliance: The DMARC failures prevent recipients from honoring unsubscribe requests, creating potential legal and compliance issues.
Key considerations
SPF record update: Laposte.net needs to update its SPF record to include Vade's sending IP addresses to ensure SPF authentication passes. This is a common solution when emails fail DMARC authentication.
DKIM alignment: Investigate if Vade can sign emails with DKIM using a selector for Laposte.net, or if Laposte.net can provide a DKIM key for Vade to use, ensuring DKIM alignment with the From domain. This is another key factor in setting up DMARC, DKIM, and SPF correctly.
Communication with Vade: Laposte.net should engage with Vade to resolve the authentication issues, as they are the sending party. This could involve updating Vade's infrastructure or the way they send emails for Laposte.net.
Monitoring DMARC reports: Regularly review DMARC reports to identify all sending sources and ensure proper authentication and alignment, allowing for proactive issue resolution.
Email marketers often face complex authentication challenges, especially when dealing with transactional emails or specialized services like unsubscribe mechanisms. The general sentiment among marketers encountering DMARC failures for critical mail flows, such as those from mailto:unsubscribe links, is one of concern regarding compliance and deliverability. They recognize the immediate impact on sender reputation and the potential legal repercussions of not honoring unsubscribe requests. The frustration often stems from relying on third-party vendors whose authentication setups may not fully align with the sender's DMARC policy, leading to unexpected failures. For more on improving deliverability, explore ultimate email deliverability guides.
Key opinions
Authentication vigilance: Marketers frequently monitor authentication results, particularly when engaging with new services or experiencing deliverability drops.
Compliance concerns: There's a strong emphasis on honoring unsubscribe requests due to legal obligations, making authentication failures for such emails particularly alarming.
Third-party reliance: Many marketers rely on external services for email sending, which can introduce complex authentication challenges if not properly configured.
Spoofing risks: Concerns exist about potential spoofing attempts that could lead to mass unsubscribe requests or other malicious activities.
Key considerations
Vendor communication: Maintaining open communication with email service providers and third-party vendors is essential to ensure proper authentication setup.
Header analysis: Understanding how to read SMTP headers is vital for diagnosing authentication issues like SPF or DKIM failures.
DMARC policy adjustments: Marketers should be aware of their domain's DMARC policy and how it affects emails failing authentication. For example, a p=reject policy would have a more severe impact than p=quarantine. Learn more about safely transitioning DMARC policies.
Legal compliance: Ensuring unsubscribe mechanisms function correctly is not just a best practice, but a legal requirement in many regions, emphasizing the urgency of resolving DMARC issues affecting them.
Marketer view
Email marketer from Email Geeks observes unsubscribe emails from Laposte.net are failing authentication. They note that a specific IP address (185.187.30.19) used by Vade is not in Laposte.net's SPF record, and their DMARC policy is set to quarantine.
28 Apr 2019 - Email Geeks
Marketer view
Email marketer from WebmasterWorld highlights that misconfigured DMARC policies can significantly hinder legitimate email delivery, even for crucial communications like unsubscribe requests. They advise regular checks of DMARC reports to spot such anomalies quickly.
15 May 2023 - WebmasterWorld
What the experts say
Email deliverability experts focus on the technical root causes of DMARC failures and the strategic implications for email senders. When faced with an issue like Laposte.net's unsubscribe emails failing DMARC, their analysis centers on the authentication chain: SPF, DKIM, and DMARC alignment. They typically look for missing or incorrect SPF records for third-party senders, unaligned DKIM signatures, and the overall impact of the DMARC policy (e.g., p=quarantine). Experts also consider the context, such as special MX records for handling specific email types, and the potential for a false positive or a useless attack vector. It is important to remember that even if DMARC authentication fails when SPF and DKIM pass, there are still ways to troubleshoot. For additional insights on email deliverability, consult comprehensive email delivery guides.
Key opinions
Authentication chain: Experts emphasize checking all authentication layers (SPF, DKIM, DMARC) for any discrepancies or misconfigurations, particularly with third-party senders.
Return-Path significance: The Return-Path domain's SPF record is crucial for DMARC SPF alignment. If it's not correctly configured, DMARC will fail.
DKIM presence: The lack of a DKIM signature or an unaligned DKIM signature for the From domain will also cause DMARC to fail.
Special handling: Some mail flows, like unsubs, might be directed to special MX records that bypass standard DMARC checks, but this doesn't resolve the underlying authentication issue for other mail receivers.
Attack vector assessment: Experts generally consider mass unsubscribe spoofing due to DMARC failure to be a useless attack, as it does not typically yield significant malicious gains for attackers.
Key considerations
Direct communication: Direct engagement with the domain owner (Laposte.net) and the third-party sender (Vade) is crucial for diagnosing and resolving the technical misconfigurations.
Header review: Thorough analysis of the full email headers is necessary to pinpoint exactly why DMARC is failing, including SPF and DKIM authentication results and alignment. More information on DMARC tags and their meanings can be helpful.
Sender responsibility: The responsibility for correct authentication configuration lies with the domain owner and their authorized senders. They must ensure all legitimate sending IPs and services are properly included in SPF records and that DKIM is correctly implemented.
Long-term monitoring: Implementing robust DMARC monitoring provides ongoing visibility into email authentication and helps prevent similar issues in the future.
Expert view
Expert from Email Geeks finds the situation interesting and states his intention to investigate further by contacting the relevant parties. This proactive approach is typical of deliverability experts.
09 Sep 2019 - Email Geeks
Expert view
Expert from SpamResource.com states that a common reason for DMARC failure with third-party senders is an SPF record that does not authorize the specific sending IP address. They recommend reviewing the SPF record and adding any missing IPs to ensure alignment.
12 Apr 2024 - SpamResource.com
What the documentation says
Official documentation and internet standards (RFCs) provide the foundational rules for email authentication, including SPF, DKIM, and DMARC. They define how domains should authorize sending sources and how receiving mail servers should process emails based on authentication results. A key principle is that for DMARC to pass, an email must pass either SPF or DKIM authentication, and the authenticating domain must align with the From header domain. Failures often indicate a breach of these defined standards, usually due to misconfiguration rather than inherent flaws in the protocols themselves. For more on the standards, consider resources on deploying DMARC for email reception.
Key findings
DMARC requirements: DMARC (RFC 7489) stipulates that an email must pass either SPF or DKIM authentication, and the domain used for that authentication must align with the From header domain for DMARC to pass.
SPF definition: SPF (RFC 7208) defines a mechanism for email senders to specify which IP addresses are authorized to send mail on behalf of a domain. Unauthorized IPs will cause SPF authentication to fail.
DKIM role: DKIM (RFC 6376) provides a method for an email sender to digitally sign an email, allowing a receiver to verify that the email was not altered in transit and was sent by an authorized sender.
Alignment modes: DMARC allows for strict or relaxed alignment modes for both SPF and DKIM. Relaxed alignment permits subdomain matches, while strict requires an exact domain match, impacting third-party sending.
Key considerations
Comprehensive SPF records: All legitimate sending sources, including third-party services, must be explicitly authorized in the domain's SPF record to ensure SPF passes. Issues can arise from broken SPF records.
DKIM implementation for third parties: When using third-party senders, ensure they can sign emails with DKIM using the organizational domain of the From header to achieve DKIM alignment.
DMARC policy application: The chosen DMARC policy (e.g., p=none, p=quarantine, or p=reject) dictates how receiving mail servers should handle emails that fail DMARC authentication. This directly impacts deliverability.
Continuous validation: Regularly validate DNS records for SPF and DKIM, and review DMARC aggregate reports to detect and rectify authentication issues promptly. This is part of maintaining best practices for email domain authentication.
Technical article
RFC 7489 (DMARC) states that for an email to pass DMARC, it must either pass SPF authentication with alignment of the SPF domain to the From header domain, or pass DKIM authentication with alignment of the DKIM domain to the From header domain.
08 Mar 2015 - RFC 7489
Technical article
RFC 7208 (SPF) outlines that an SPF record specifies which hosts are authorized to send mail for a domain. If an email is sent from an IP address not listed in the SPF record, it will typically result in an SPF fail.
