Does DMARC validation occur before or after email delivery?
Michael Ko
Co-founder & CEO, Suped
Published 23 Jul 2025
Updated 28 Sep 2025
7 min read
The question of whether DMARC validation occurs before or after email delivery is fundamental to understanding how this crucial email authentication protocol functions. It's a common point of confusion, but getting the timing right reveals a lot about DMARC's effectiveness in preventing email fraud and enhancing deliverability.
DMARC, or Domain-based Message Authentication, Reporting, and Conformance, builds upon SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) to provide a comprehensive framework for domain owners to protect their brand from spoofing and phishing attacks. Its primary goal is to tell receiving email servers what to do with emails that fail authentication, rather than simply identifying them as suspicious.
Understanding when DMARC validation takes place is key to appreciating its role in the email ecosystem, safeguarding both senders and recipients. Let's explore the process of how an email travels and where DMARC fits into that journey.
The journey of an email and DMARC's interception point
When an email is sent, it first travels from the sender's mail server to the recipient's mail server. Before the email even gets a chance to land in an inbox, the receiving mail server performs a series of checks. These initial checks are critical to filter out spam, malicious content, and unauthorized senders. Among these checks are the validations for SPF and DKIM, which are the foundational authentication protocols for DMARC.
The receiving server checks the sender's SPF record to verify that the sending IP address is authorized to send mail on behalf of the domain. Concurrently, it verifies the DKIM signature attached to the email to ensure the message hasn't been tampered with in transit. These two validations occur right at the point of acceptance, during the SMTP conversation between servers. If either SPF or DKIM (or both) pass and align with the From header domain, then the email has a good chance of passing DMARC.
Example DMARC DNS RecordDNS
_dmarc.yourdomain.com IN TXT "v=DMARC1; p=quarantine; rua=mailto:reports@yourdomain.com; ruf=mailto:forensic@yourdomain.com; fo=1; aspf=r; adkim=r;"
DMARC validation happens immediately after these initial SPF and DKIM checks, but crucially, still before the email is delivered to the recipient's inbox. The receiving mail server queries the sender's DNS for the DMARC record to determine the policy for handling messages that fail SPF or DKIM alignment. This means DMARC provides instructions on whether to reject, quarantine, or monitor such emails. Therefore, DMARC validation is an integral part of the email receiving process, taking place at the gateway of the recipient's mail system.
How DMARC validation works in real time
The core of DMARC validation lies in alignment. For an email to pass DMARC, it must pass either SPF or DKIM authentication, and importantly, the domain used in the authentication (SPF's MailFrom domain or DKIM's d= domain) must align with the domain in the visible From header. This alignment check is performed by the receiving mail server in real-time, as it processes the incoming email.
If an email fails DMARC validation, the receiving server then consults the DMARC policy (p=none, p=quarantine, or p=reject) published in the sender's DNS record. Based on this policy, the email will either be delivered to the inbox (p=none), sent to the spam or junk folder (p=quarantine), or blocked entirely (p=reject). This action is taken before the email is considered delivered to the end-user's mailbox. For instance, Google Workspace admin help notes that DMARC tells receiving servers what to do with messages that don't pass authentication.
Before DMARC Policy Enforcement
Suspicious email: Emails failing SPF or DKIM might still reach the inbox or spam folder without clear instructions, making spoofing easier.
Lack of control: Domain owners have limited control over how receiving servers handle unauthenticated emails.
Increased risk: Higher vulnerability to phishing and impersonation attacks, harming brand reputation.
After DMARC Policy Enforcement
Clear instructions: DMARC tells receiving servers how to handle emails that fail authentication, such as rejecting them outright.
Enhanced control: Domain owners define the policy for unauthenticated emails, regaining control over their domain's email use.
Reduced fraud: Significantly reduces spam, phishing, and business email compromise (BEC) attacks, as noted by Microsoft Defender.
This pre-delivery validation means that DMARC acts as a gatekeeper, preventing fraudulent emails from ever reaching a recipient's inbox. If an email's authentication fails, and the DMARC policy is set to quarantine or reject, it will not be considered delivered in the traditional sense. This is critical for maintaining a clean and secure email channel, and it underscores the preventative nature of DMARC.
Impact on email deliverability and security
The fact that DMARC validation occurs before delivery has significant implications for both email deliverability and security. For legitimate senders, a correctly configured DMARC policy (especially at p=quarantine or p=reject) signals to receiving mail servers that your domain is actively protected. This can improve your domain's reputation, increasing the likelihood that your legitimate emails will reach the inbox. Conversely, failing DMARC validation, particularly if your policy is enforced, means those emails will likely be blocked or quarantined, protecting recipients from potential phishing and spoofing attacks.
Monitoring DMARC reports is essential to understand how your emails are performing against your policy. These reports provide invaluable insights into authentication failures and legitimate sending sources, allowing you to fine-tune your SPF and DKIM records. Without DMARC, you lose visibility into emails sent using your domain that aren't authenticated, leaving you vulnerable to impersonation. This is why DMARC monitoring is a critical practice for any domain owner.
Best practice for DMARC policy enforcement
Start with a DMARC policy of p=none to collect reports without affecting email delivery. Analyze these reports to identify all legitimate sending sources and ensure their SPF and DKIM are properly configured and aligned. Only then should you incrementally move to p=quarantine and finally p=reject. This phased approach minimizes disruption to your legitimate email flow.
Ultimately, a strong DMARC policy, alongside properly configured SPF and DKIM, ensures that your authentic emails are trusted and delivered, while impersonating emails are efficiently blocked. This proactive validation mechanism is a cornerstone of modern email security, protecting your brand's reputation and your recipients from email-borne threats.
Maximizing your email authentication
To summarize, DMARC validation unequivocally occurs before an email is delivered to a recipient's inbox. It is a critical, real-time check performed by the receiving mail server that dictates the fate of an incoming email based on its authentication status and the sender's published policy. This pre-delivery action is what gives DMARC its power as a security and deliverability protocol, allowing domain owners to enforce how their domain is used for email.
By stopping unauthenticated emails at the gate, DMARC helps to clean up the email ecosystem, reducing the volume of spam and malicious emails that ever reach users. This not only protects individual recipients but also helps to build trust in email as a communication channel for businesses and organizations worldwide. Without DMARC, the internet would be a far more dangerous place for email users, making it a foundational element of a robust email security posture.
Effectively managing DMARC, especially when dealing with complex sending infrastructures or multiple domains, can be challenging. This is where tools like Suped come into play. Our platform provides AI-powered recommendations to simplify policy enforcement, real-time alerts for immediate issue detection, and a unified dashboard for all your DMARC, SPF, and DKIM monitoring needs. We also offer SPF flattening and a multi-tenancy dashboard for MSPs, making DMARC accessible and actionable for everyone.
With our focus on simplicity, actionable insights, and a feature-rich free plan, Suped empowers you to achieve a p=reject policy with confidence, securing your email communication and maximizing your deliverability.
