Why is Virgin Media bouncing emails with 'Header From domain is invalid' error, and how to fix it?

Key findings

• Root cause: The 'Header From domain is invalid' error from Virgin Media is primarily caused by the absence of MX or A records for the sending domain.
• Policy change: Virgin Media appears to have recently implemented stricter email policies, leading to overnight blocking for domains that previously sent successfully despite lacking necessary DNS records. This mirrors a broader trend among mailbox providers. Learn more about why emails are going to spam.
• Error message ambiguity: The error message itself can be misleading, as it points to the 'Header From' domain but the actual solution involves foundational DNS configurations for the sending domain.
• DMARC relevance: While not the direct cause of this specific error, the absence of a DMARC record often accompanies domains lacking proper MX or A records, indicating a general neglect of modern email authentication standards. Understanding DMARC, SPF, and DKIM is crucial for overall deliverability.

Key considerations

• DNS configuration: Ensure all sending domains, including subdomains used for email, have correctly configured MX and A records. This is fundamental for email servers to locate and validate the sending domain.
• Proactive approach: Implement a default A record for both the visible 'From' domain and return-path subdomain. This helps pre-empt issues with smaller ISPs that might have specific, seemingly arbitrary, A record requirements. This is part of maintaining a robust email deliverability strategy.
• Legacy client challenges: For older clients with entrenched systems, it can be difficult to enforce updates until deliverability issues force their hand. Frame the need for DNS updates as compliance with current industry standards.
• Postmaster unresponsiveness: Be prepared for unresponsiveness from some ISPs' postmaster teams. Focusing on internal DNS and authentication fixes is often more effective than relying on external support for this particular error.
• Comprehensive authentication: Beyond MX and A records, ensure full implementation of SPF, DKIM, and DMARC. These protocols are essential for proving your emails are legitimate and can prevent bouncing due to authentication failures or 'invalid sender domain' errors. See more on why emails are bouncing with 'domain does not exist' errors.

Key opinions

• Policy shift: Marketers widely believe Virgin Media has recently changed its email filtering policies, as several previously unaffected senders are now experiencing this bounce. This suggests a tightening of requirements for domain validation.
• Forced compliance: The pain of deliverability issues is often the only catalyst for companies, particularly legacy clients, to adopt modern best practices like implementing DMARC or proper DNS records.
• DNS records are fundamental: The primary suspicion among marketers is that the lack of MX and A records is the culprit, rather than DMARC, though DMARC is still a crucial component for overall email health. It's a foundational step that can help avoid various bounce types, including 'invalid domain name' errors as noted by Kickbox.
• Legacy domain challenges: Dealing with clients who use 'cousin domains' or simply neglect DNS management due to historical setups is a recurring challenge, often requiring direct communication about critical updates.

Key considerations

• Client communication: Clearly communicate to clients that DNS records (MX, A) and DMARC are no longer optional for reliable email delivery, especially with evolving ISP requirements. Highlight that these are now industry standards.
• Proactive auditing: Regularly audit client DNS settings, particularly for older clients, to identify and rectify missing records before they lead to deliverability issues. This can help prevent bounces to Tiscali.it or similar providers.
• Standardize setup: Incorporate MX and A record setup, along with DMARC, as a standard part of onboarding new clients. This prevents future issues with evolving deliverability standards.
• Domain strategy: Advise clients against using 'cousin domains' or non-standard sending domains without ensuring they have full DNS control and proper record configuration. This is key to a healthy email sending setup.

Key opinions

• MX/A record as culprit: Experts largely concur that the absence of MX or A records for the sending domain is the most probable cause of the Virgin Media error, despite the vague wording of the bounce message.
• DMARC secondary: While important for reputation, DMARC is considered less likely to be the direct reason for this specific bounce compared to the foundational MX/A record issue, as much non-DMARC compliant mail still gets through globally.
• Proactive DNS: To avoid future issues, experts advise implementing both A and MX records as standard for all sending domains, including subdomains or 'cousin domains', even if an ISP doesn't explicitly require them. This is a robust approach to prevent unexpected rejections from various mailbox providers. You can also test your email deliverability.
• ISP policy evolution: It's plausible that ISPs like Virgin Media are increasingly checking for basic DNS records as part of their anti-abuse or anti-spoofing efforts, triggering blocks for domains that previously flew under the radar.

Key considerations

• Fundamental DNS health: Emphasize to clients that proper DNS configuration is a non-negotiable foundation for email deliverability. A missing MX or A record for a sending domain is a significant gap in setup, regardless of the specific bounce message. This ties into core concepts of boosting email deliverability.
• Gradual policy rollout: Some ISPs might not check for MX/A records constantly but might trigger checks when specific conditions are met, such as an NXDomain response during mail delivery. This could explain why older configurations suddenly start failing.
• Comprehensive authentication stack: While MX/A records address the immediate issue, ensure SPF, DKIM, and DMARC are all correctly implemented. These layers of authentication work together to build domain reputation and prevent emails from being blocked or sent to spam, even addressing DMARC verification failures.
• Cost-benefit of DNS queries: It is generally more resource-efficient for an ISP to perform an additional DNS query during mail delivery than to maintain a persistent state for every sender to track their DNS compliance.

Key findings

• DNS resolution is mandatory: According to RFC standards, any domain used in email headers (including the 'From' address) must be resolvable in DNS. This means having appropriate A or MX records to indicate its existence and, optionally, its mail-handling capabilities.
• MX records for mail handling: MX records are specifically designed to tell other mail servers where to send email for a given domain. While an A record can provide basic host resolution, an MX record signals that the domain is set up for mail exchange. Read about SPF DNS timeouts at Microsoft.
• Invalid domain checks: Mail servers perform various checks on the 'Header From' domain, including verifying its existence and validity in DNS. Failure to resolve these records triggers errors like 'domain is invalid' or 'domain does not exist'.
• Authentication standards: While this specific error points to DNS, the broader context of modern email deliverability includes robust authentication (SPF, DKIM, DMARC). These standards rely on proper DNS configuration to function correctly and prevent spoofing. Understand advanced email authentication.

Key considerations

• RFC compliance: Adherence to internet standards (RFCs) is fundamental for interoperability in email systems. Domains failing basic DNS resolution are non-compliant and will face increasing scrutiny and rejection from receiving mail servers.
• Sender reputation impact: Failing fundamental DNS checks can negatively impact a sender's domain reputation, leading to further blocks or spam folder placement, even if other factors are in order.
• DNS propagation: After adding or modifying DNS records, allow sufficient time for propagation (up to 48 hours, though often faster) before retesting. ISPs rely on cached DNS information, so immediate changes might not be reflected globally.
• Monitoring and logging: Regularly monitor bounce logs for specific error codes. This helps identify new policy changes from ISPs or emerging technical issues that might not be immediately apparent. For instance, error messages can guide troubleshooting.