Can I set DMARC to reject if my domain doesn't send email?
Michael Ko
Co-founder & CEO, Suped
Published 12 Aug 2025
Updated 19 Aug 2025
7 min read
It's a common scenario in many organizations: you have domains registered that are used for your website, internal applications, or simply as placeholders, but they never send email. Yet, a DMARC (Domain-based Message Authentication, Reporting, and Conformance) checker tool might flag these domains for not having a DMARC record, or for having a weak policy. This raises an important question: can I set a DMARC policy of p=reject for a domain that doesn't send email?
The short answer is yes, you absolutely can, and in most cases, you should. Implementing a strict DMARC policy, such as p=reject, for domains that are not intended to send email is a powerful security measure. It acts as a clear signal to receiving mail servers that any email claiming to be from your domain, but failing DMARC authentication, should be blocked entirely.
This approach is highly recommended for protecting your brand and preventing abuse, even if the domain is not actively used for outgoing communications. It closes a potential backdoor that phishers and spammers could exploit to impersonate your organization, safeguarding your reputation and that of your legitimate email-sending domains.
Even if a domain isn't used for sending legitimate emails, it can still be a target for malicious actors. Cybercriminals often exploit unprotected domains (especially those with no DMARC, SPF, or DKIM records) to launch phishing attacks or send spam. They might spoof your domain, making it appear as if the emails originate from your organization.
When such spoofed emails reach recipients, they can damage your brand's reputation, lead to customer confusion, or even result in financial losses if successful phishing attempts occur. This is why securing all your domains, regardless of their primary function, is crucial for comprehensive email security.
By implementing DMARC with a p=reject policy, you're instructing email providers worldwide to reject any email that claims to be from your domain but fails DMARC authentication. This prevents unauthorized emails from ever reaching recipients' inboxes, effectively eliminating the threat of domain spoofing for that particular domain. Protecting domains that do not send email is a proactive and smart move.
The risk of unprotected domains
Brand impersonation: Attackers can use your domain to send fraudulent emails, damaging trust in your brand.
Phishing and malware: Spoofed emails can deliver malware or trick recipients into revealing sensitive information.
Blacklisting: Even if you don't send legitimate emails, your domain could end up on an email blocklist (or blacklist) due to abuse.
Compliance issues: Many compliance frameworks recommend or require DMARC implementation across all domains for enhanced security.
Understanding DMARC policies for non-sending domains
DMARC policies come in three main types: p=none (monitoring), p=quarantine (send to spam/junk), and p=reject (block completely). For domains that actively send email, a phased DMARC implementation, starting with p=none to gather data, is often recommended before moving to stricter policies. However, for domains that are definitively not sending emails, this cautious approach isn't necessary.
If you're certain a domain (and its subdomains) will never legitimately send email, you can set its DMARC policy directly to p=reject from day one. This simplifies the deployment process considerably, as there's no need to monitor reports for legitimate email streams that might be affected. The goal is simply to prevent any unauthorized usage. This is outlined further in how to protect domains that do not send email.
Setting p=reject for a non-sending domain provides the strongest level of protection against spoofing. It tells email receivers that any messages appearing to come from your domain are illegitimate if they fail DMARC, and those receivers should be outright rejected. This significantly reduces the risk of your domain being used for phishing or spam campaigns.
Standard DMARC deployment
Typically, you'd start with a p=none policy to monitor email streams and identify all legitimate sending sources. This phase can take weeks or months.
Gradually, you would move to p=quarantine and then p=reject once confident that all legitimate emails pass authentication.
DMARC for non-sending domains
If you are absolutely certain that no email, not even internal system alerts or contact form submissions, will ever originate from the domain or its subdomains, you can set p=reject immediately.
This policy provides immediate, strong protection against domain spoofing and abuse, making it highly effective for defensive purposes.
Implementing DMARC for a non-sending domain
Before you set your DMARC record to p=reject, the most critical step is to perform a thorough audit to ensure no legitimate email is being sent from that domain or any of its subdomains. This includes checking:
Website contact forms: Do they send notifications using the domain in the 'From' address?
Internal systems: Are there any automated alerts, error reports, or notifications sent from the domain?
Third-party services: Are any marketing automation platforms, CRMs, or other tools configured to send emails using this domain?
Once you've confirmed that no legitimate email is being sent (or will be sent) from the domain, creating the DMARC record is straightforward. You'll add a TXT record to your DNS for the domain.
In this example, p=reject tells receiving servers to reject emails that fail DMARC. sp=reject applies the same policy to subdomains. The rua tag is optional but highly recommended. It specifies an email address where aggregate DMARC reports should be sent. While you might not expect reports for a non-sending domain, these reports can alert you to any unexpected email activity using your domain, including potential spoofing attempts. The Microsoft Defender documentation provides more context on DMARC configuration and authentication.
You might also consider adding simple SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) records, even though DMARC with p=reject will handle authentication failures. For SPF, you could use a record like v=spf1 -all, explicitly stating that no servers are authorized to send email for your domain.
What to watch out for
While setting DMARC to p=reject for a non-sending domain is generally safe and highly effective, there are a few considerations to keep in mind. The primary concern is ensuring that no legitimate email is, or ever will be, sent from that domain without proper authentication. Any unforeseen email streams would be immediately rejected, leading to deliverability issues.
It's also essential to communicate this policy internally, especially with IT and marketing teams, to prevent future configurations that might inadvertently attempt to send email from the domain. Clear documentation of your DMARC strategy for non-sending domains can prevent future headaches and ensure everyone is aware of the intended behavior. This also helps with configuring DMARC, SPF, and DKIM.
Finally, even with a reject policy, continue to monitor your DMARC reports (if you configure the rua tag). These reports, even if sparse, can provide valuable insights into any unexpected email flows or active spoofing attempts that might be targeting your domain, helping you stay on top of your email security posture and potentially avoid getting your domains added to an email blacklist (or blocklist).
Views from the trenches
Best practices
Ensure a thorough audit for any unforeseen email sending activity from the domain before setting p=reject.
Communicate the DMARC p=reject policy for non-sending domains to all relevant internal teams, including IT and marketing.
Use the 'sp=reject' tag in your DMARC record to apply the reject policy to any subdomains of the non-sending domain.
Common pitfalls
Setting p=reject without confirming that absolutely no legitimate email is sent from the domain, leading to unexpected rejections.
Forgetting to include the 'sp=reject' tag, which could leave subdomains vulnerable to spoofing.
Not monitoring DMARC reports (even sparse ones) for non-sending domains, missing early signs of abuse.
Expert tips
For domains explicitly not used for email, a direct p=reject deployment saves time and resources compared to a gradual rollout.
Even if a domain never sends email, a DMARC p=reject policy is a strong signal to mail receivers to block all unauthorized usage.
Engage with system administrators or hosting providers when implementing DMARC to identify potential hidden email sending processes.
Expert view
An expert from Email Geeks says that setting a DMARC p=reject policy is effective, provided no mail is sent from the main domain, any subdomains, or superdomains in the 'From' address.
2020-09-22 - Email Geeks
Marketer view
A marketer from Email Geeks suggests reviewing all potential sources like contact forms, CRM integrations, and web servers to ensure no email is unknowingly sent from the domain.
2020-09-22 - Email Geeks
Key takeaways
Setting a DMARC p=reject policy for domains that do not send email is not just permissible, but it's a recommended best practice for bolstering your organization's overall email security. It offers immediate and strong protection against domain spoofing and phishing attempts, even for dormant or non-operational email domains.
By taking this proactive step, you simplify DMARC implementation and significantly reduce the attack surface for bad actors, contributing to a more secure email ecosystem for your brand and its recipients. Always ensure a thorough audit and clear internal communication before deployment to avoid any unintended disruptions.
