What should you do if your emails use a domain in the Message-ID that you do not own and is on a blocklist?
Matthew Whittaker
Co-founder & CTO, Suped
Published 15 Apr 2025
Updated 15 Aug 2025
7 min read
Dealing with email deliverability issues can be incredibly frustrating, especially when the problem stems from something as technical as a `Message-ID` header. I've encountered situations where organizations inadvertently use domains they don't own within their email headers, and then discover these domains are listed on major blocklists (or blacklists), like Spamhaus DBL. This scenario can lead to significant email delivery failures, particularly with prominent mailbox providers like Microsoft Office 365. It's a tricky situation because you lack direct control over a domain you don't own, making de-listing efforts nearly impossible.
The `Message-ID` header is a unique identifier for an email, designed to prevent duplicate messages and aid in tracking. While it's largely for internal mail system use, some anti-spam filters, especially those concerned with domain reputation and authenticity, do check the domain part of the `Message-ID`.
When the domain in your `Message-ID` is on a blocklist (or blacklist), it signals to recipient servers that your email might be associated with spam or malicious activity. Even if your sending domain (the 'From' address) is legitimate and properly authenticated, the presence of a blacklisted domain in the `Message-ID` can cause your emails to be rejected or routed to the spam folder. This is particularly true for strict receivers like Microsoft and Gmail, which are vigilant about protecting their users.
The primary issue here is the use of a domain that is not owned by the sender. This is a critical departure from standard email practices and RFC compliance. Email RFCs (Request for Comments) define how email systems should operate, and using unowned domains in headers undermines the trust model. Without ownership, you cannot manage the domain's DNS records, which are vital for email authentication protocols like SPF, DKIM, and DMARC.
Unowned domains, especially parked domains, are frequently targeted by spammers and can end up on blocklists (or blacklists) due to misuse by various parties. Because the legitimate owner of a parked domain might not be actively monitoring it or its reputation, it becomes an easy target for abuse. If your `Message-ID` contains such a domain, you inherit its poor reputation and the associated deliverability challenges.
Trying to get an unowned domain removed from a blacklist (or blocklist) is typically a futile effort. Blacklist operators like Spamhaus (specifically their DBL, or Domain Blocklist) will only communicate with the domain owner. If you don't own the domain, you have no standing to request de-listing or remediation. This highlights the critical importance of maintaining control over all domains used in your email headers.
Why it's a problem
Using a domain you don't own in your `Message-ID` header is a severe misconfiguration. It violates email standards and can lead to persistent deliverability issues, as you cannot control the reputation or blocklist status of a third-party domain.
Resolving the deliverability problem
The most straightforward and effective solution is to immediately stop using the unowned, blocklisted domain in your `Message-ID`. While it might seem like a daunting change, especially if it's been a long-standing practice, it's the only way to genuinely resolve the root cause of the deliverability problems. You need to configure your mail system to generate `Message-ID` headers with a domain you own and control, ideally your primary sending domain or a subdomain thereof.
After making this change, it's crucial to review your overall email authentication setup. Ensure your SPF, DKIM, and DMARC records are correctly configured for your owned sending domains. Proper authentication helps build a positive sender reputation and signals to recipient servers that your emails are legitimate. You can learn more about these protocols in our simple guide to DMARC, SPF, and DKIM.
I also recommend actively monitoring your domain's reputation and any blocklist (or blacklist) listings. Tools that provide blocklist monitoring can alert you quickly if your domains or IPs appear on any blacklists. For issues specific to Microsoft domains, direct engagement with their support might be necessary after you've fixed your `Message-ID`.
The problem
Unowned domain in Message-ID: Your emails use a domain you do not control in the `Message-ID` header, like `example.net`.
Blacklisted status: This unowned domain is on a public blacklist (or blocklist), such as Spamhaus DBL, due to past abuse or its nature as a parked domain.
Deliverability impact: Emails are being rejected or sent to spam, primarily by strict receivers like Microsoft.
No control: You cannot request de-listing from the blacklist because you do not own the problematic domain.
The solution
Immediate action: Configure your email system to use a domain you own for the `Message-ID` header, such as `yourdomain.com` or a subdomain.
Authentication check: Verify and strengthen your SPF, DKIM, and DMARC records for all sending domains.
Communication: If issues persist, reach out to specific ISPs or mailbox providers (Microsoft, etc.) to explain the remedied situation.
Moving forward and maintaining reputation
Once you've changed your `Message-ID` to use a domain you own, the impact of the old, blacklisted domain should gradually diminish. Mailbox providers that were blocking your emails based on the `Message-ID` will start seeing a clean, owned domain. This change, combined with proper email authentication like SPF, DKIM, and DMARC, will help rebuild your sender reputation.
For domains you don't own that are on blocklists (or blacklists), there's little you can do directly. The onus is on the actual owner of that domain to address the listing. Your only actionable step is to ensure your email sending infrastructure no longer references or relies on such external, problematic domains in any way.
This situation underscores the importance of a holistic approach to email deliverability. It's not just about what's in your 'From' address, but also the underlying technical headers that mail servers scrutinize. Ensuring every aspect of your email, from content to technical configuration, aligns with best practices is crucial for consistent inbox placement.
Example of a correct Message-ID header
Message-ID: <unique-string@your-owned-domain.com>
Navigating blacklists with unowned domains
Resolving issues with domains you don't own on blocklists means focusing on what you can control. Here's a quick reference for common actions and their feasibility:
Action
Feasibility when domain is unowned
Notes
Change Message-ID domain
Yes
This is the primary and most effective fix you can implement.
Request de-listing from blocklist
No
Blocklist operators (e.g., Spamhaus) only work with the domain owner.
Improve domain authentication (SPF, DKIM, DMARC)
Yes (for your owned domains)
Crucial for rebuilding your sender reputation with your own legitimate domains.
Communicate with affected ISPs
Limited Yes
You can inform them of the `Message-ID` change, but direct de-listing of the unowned domain is not possible.
This table underscores the primary strategy: fix what you control and adapt to the reality that you can't intervene on behalf of a domain you don't own. Focus on your own domains' health.
Views from the trenches
Best practices
Always use domains you own and control in all email headers, including the Message-ID, to ensure full compliance and manageability.
Implement and monitor DMARC policies at p=quarantine or p=reject to gain visibility and control over your sending domains.
Regularly check your domain and IP reputation using a reliable blocklist checker to proactively identify and address any listings.
Educate your team on email sending best practices to avoid inadvertent configurations that could lead to deliverability issues.
Common pitfalls
Attempting to delist a domain from a blocklist when you are not its legitimate owner, which will always be unsuccessful.
Ignoring Message-ID domains, assuming they are purely internal and have no impact on external email deliverability.
Delaying the necessary configuration changes, prolonging deliverability issues and potentially damaging your overall sender reputation.
Failing to set up proper SPF, DKIM, and DMARC for all sending domains, leaving authentication gaps that can harm deliverability.
Expert tips
Ensure your mail transfer agent (MTA) or email service provider is configured to generate the Message-ID correctly with your domain.
If using a third-party sending service, confirm that they are not introducing unowned domains into your Message-ID headers.
For legacy systems, prioritize updating the Message-ID generation logic, even if it requires significant development effort.
Remember that even if a domain is 'parked,' it can still be blacklisted if it's been used for spam, and this affects anything referencing it.
Expert view
Expert from Email Geeks says: You must first understand the specific reason why the unowned domain is listed on the Spamhaus DBL before attempting any changes, as the listing reason is never random.
2020-04-01 - Email Geeks
Expert view
Expert from Email Geeks says: It's crucial to review the listing reason for the domain in the DBL, fix the underlying cause, and then establish DMARC with careful monitoring of reports for any anomalies. Simply changing domains is rarely the complete answer.
2020-04-01 - Email Geeks
The path to better deliverability
Ultimately, if your emails are using an unowned domain in the `Message-ID` that is on a blocklist (or blacklist), the path forward is clear, albeit potentially challenging in terms of implementation. You must transition away from using the problematic domain in your email headers. This fundamental change, coupled with a robust email authentication setup for your owned domains, is the only sustainable way to restore and maintain good email deliverability.
While it might seem easier to find workarounds, direct engagement with blocklist operators for domains you don't own is impossible. The focus must be on bringing your email practices into full compliance with industry standards, ensuring that every element of your outgoing mail—from the visible 'From' address to the technical `Message-ID`—reflects your legitimate sending identity. This commitment to proper configuration will safeguard your sender reputation and ensure your emails reach their intended inboxes.
Microsoft Office 365. It's a tricky situation because you lack direct control over a domain you don't own, making de-listing efforts nearly impossible.
Spamhaus
0Spam
Cisco
NoSolicitado
URIBL
abuse.ro
ALPHANET
Anonmails
Ascams
BLOCKEDSERVERS
Calivent Networks
EFnet
JustSpam
Kempt.net
NordSpam
RV-SOFT Technology
Scientific Spam
Spamikaze
SpamRATS
SPFBL
Suomispam
System 5 Hosting
Team Cymru
Validity
www.blocklist.de Fail2Ban-Reporting Service
ZapBL
2stepback.dk
Fayntic Services
ORB UK
technoirc.org
TechTheft
Microsoft domains, direct engagement with their support might be necessary after you've fixed your `Message-ID`.
