Why are ESPs enforcing DMARC policies and what are the implications?
Matthew Whittaker
Co-founder & CTO, Suped
Published 17 Jun 2025
Updated 15 Aug 2025
9 min read
Over the past year, we've seen a noticeable shift in how Email Service Providers (ESPs) are handling DMARC. Once a recommendation, DMARC is rapidly becoming a mandatory requirement, particularly with the stricter authentication rules imposed by major mailbox providers like Gmail and Yahoo Mail. This proactive stance by ESPs is a significant development, and it has profound implications for anyone sending emails, from large enterprises to small businesses.
The core of this change stems from a collective effort to combat email-based threats, such as phishing and spoofing. By enforcing DMARC, ESPs aim to create a more secure email ecosystem, protecting both their users and the reputation of their sending infrastructure. It means we, as senders, must ensure our email authentication is robust or risk our messages not reaching their intended recipients.
One of the primary drivers behind ESPs mandating DMARC is the increasing sophistication of phishing and spoofing attacks. These attacks leverage domain impersonation to trick recipients, leading to data breaches, financial losses, and significant damage to brand reputation. DMARC provides a crucial layer of defense by allowing domain owners to tell receiving mail servers how to handle emails that claim to be from their domain but fail authentication checks, specifically SPF and DKIM. This tells mail receivers what to do when emails fail checks. You can learn more about how DMARC works with SPF and DKIM.
ESPs are also responding to direct mandates from large mailbox providers. Both Google and Yahoo announced new requirements for bulk senders, making DMARC enforcement a critical component for maintaining good deliverability. These requirements push for a minimum DMARC policy of p=quarantine or p=reject, effectively pushing the responsibility of strong authentication onto the senders and their ESPs. We also have to comply with Microsoft's new sender requirements.
For ESPs, it's also about maintaining their own sending reputation. If their clients are consistently sending unauthenticated or spoofed emails, it can lead to their shared IP addresses and domains being added to email blocklists (or blacklists), impacting deliverability for all their customers. By ensuring DMARC compliance, ESPs mitigate this risk and safeguard their infrastructure's trustworthiness. This protects their reputation and the deliverability of their entire client base. It is for this reason that some ESPs are forcing DMARC on their paid customers.
Increased trust and security
Brand protection: DMARC helps prevent unauthorized parties from sending emails using your domain, safeguarding your brand's reputation from phishing and spoofing attacks.
Enhanced security: It strengthens email security for recipients by ensuring that messages claiming to be from your domain are legitimate.
Industry compliance: Meeting the DMARC requirements of major mailbox providers is essential for email deliverability today.
Finally, DMARC's reporting capabilities are invaluable for ESPs. DMARC reports provide aggregated and forensic data on email authentication failures. This data helps ESPs (and domain owners) identify legitimate sending sources that might not be properly authenticated and detect malicious activity attempting to spoof their clients' domains. This level of visibility is crucial for proactive domain management and threat mitigation.
The impact on sender reputation and deliverability
The enforcement of DMARC policies by ESPs has direct and significant implications for sender reputation and email deliverability. For senders, proper DMARC implementation is no longer optional, especially for those sending a high volume of emails. If your domain's DMARC policy is not properly configured, or if your emails fail SPF or DKIM alignment, they are likely to be rejected or sent to the spam folder. This directly impacts your ability to reach your audience and can severely harm your domain's reputation.
A strong DMARC policy (p=quarantine or p=reject) signals to mailbox providers that you are serious about email security. This commitment builds trust and can positively influence your sender reputation. Conversely, ignoring DMARC or maintaining a p=none policy can lead to increased scrutiny from mail servers, potentially resulting in your legitimate emails being treated as suspicious. It also leaves your brand vulnerable to impersonation, as bad actors can easily spoof your domain without fear of immediate rejection. This impacts your overall email deliverability and engagement.
Before DMARC enforcement
Vulnerability: Domain is susceptible to phishing and spoofing, leading to brand misuse.
Inconsistent deliverability: Legitimate emails may still end up in spam or be rejected, especially by stricter receivers.
Lack of visibility: No insight into unauthorized use of your domain for email sending.
Improved inbox placement: Higher authentication rates lead to better sender reputation and deliverability. Read more about how it improves email deliverability.
Actionable insights: DMARC reports offer data on email streams, helping identify authentication issues.
The shift also indirectly supports initiatives like BIMI (Brand Indicators for Message Identification). While BIMI itself is a carrot for senders, offering visual brand recognition in inboxes, it requires a DMARC policy of p=quarantine or p=reject to implement. By pushing for DMARC enforcement, ESPs are inadvertently (or intentionally) making it easier for brands to adopt BIMI, thereby enhancing brand trust and engagement directly within the inbox, as BIMI's FAQ explains.
Implications for domain owners and marketers
While ESPs enforcing DMARC offers significant benefits, it also presents challenges for domain owners and marketers. The primary concern arises when a domain sends emails through multiple services. If an ESP automatically enforces a DMARC policy for a subdomain, it can create conflicts if another service attempts to send from the same subdomain without proper authentication. This can lead to unexpected email rejections or misdirection to spam folders, causing frustration and impacting campaigns.
Another implication is the need for proactive DMARC management. If your ESP sets up a p=reject policy without DMARC reporting enabled (the rua tag in your DMARC record), you lose critical visibility. Without reports, you won't know if legitimate emails are failing authentication or if malicious actors are attempting to spoof your domain. This lack of insight can make it challenging to troubleshoot deliverability issues and maintain a healthy sending reputation. This is why it's so important to understand DMARC implementation challenges.
The balance between security and control becomes a key consideration. While automatic DMARC enforcement by ESPs simplifies setup for many, it can remove some control from the domain owner. Marketers, in particular, need to be aware of these policies to avoid disruptions to their email campaigns. It's crucial to collaborate with your ESP to understand their DMARC practices and ensure your overall email sending strategy aligns with these new requirements.
Here's an example of a DMARC record that includes reporting, which provides crucial visibility into your email streams:
To navigate the landscape of ESP-enforced DMARC policies effectively, domain owners and marketers need a proactive approach. Start by understanding your current DMARC posture. Use a DMARC record generator to check if you have a DMARC record, and if so, what policy (p=none, p=quarantine, or p=reject) is applied. If you're starting fresh, it's generally recommended to begin with p=none and gradually move towards enforcement, especially if you have complex sending infrastructure. We provide a guide on how to safely transition your DMARC policy that can help.
Always ensure that DMARC reporting (using the rua and ruf tags) is configured. These reports provide invaluable data that helps you identify all legitimate sending sources for your domain and pinpoint any unauthorized attempts to spoof your brand. Monitoring these reports is key to moving to a stricter DMARC policy without negatively impacting your email deliverability. For more guidance, check out our resource on why businesses need DMARC.
Collaborate closely with all your ESPs to understand their DMARC practices for subdomains and shared IPs. Ensure that any services sending on your behalf are properly authenticated with SPF and DKIM and align with your DMARC policy. This collaborative approach will help you avoid unexpected deliverability issues and maintain a strong, secure email presence. Having the right DMARC settings and understanding the implications of using p=reject is critical.
Views from the trenches
Best practices
Always include 'rua' and 'ruf' tags in your DMARC record to receive valuable reports on email authentication.
Start with a DMARC 'p=none' policy to monitor email streams and identify all legitimate senders before moving to stricter policies.
Ensure all sending services are properly authenticated with SPF and DKIM before enforcing DMARC to avoid deliverability issues.
Regularly review your DMARC reports to detect unauthorized email sending and troubleshoot any authentication failures.
Common pitfalls
Implementing 'p=reject' without prior monitoring can lead to legitimate emails being blocked.
Failing to account for third-party senders (e.g., transactional email providers) in your DMARC policy.
Not understanding the difference between SPF/DKIM alignment and overall DMARC policy enforcement.
Ignoring DMARC reports, thus missing critical insights into email security and deliverability.
Expert tips
Consider using dedicated subdomains for different sending purposes (e.g., marketing, transactional) to simplify DMARC management and reduce conflicts.
For complex sending environments, a DMARC monitoring platform can automate report analysis and provide actionable insights.
Educate your team, especially marketing and IT, about the importance of DMARC and proper email sending practices.
Remember that BIMI requires a DMARC policy of 'p=quarantine' or 'p=reject' for your logo to display in supporting inboxes.
Expert view
Expert from Email Geeks says they've seen a few ESPs automatically set up DMARC records for clients and while it's good, a default 'p=reject' without reporting can be reckless.
2020-06-26 - Email Geeks
Marketer view
Marketer from Email Geeks says that while it's good that ESPs are enforcing DMARC for unique subdomains, lacking reporting or control can be frustrating.
2020-06-26 - Email Geeks
Embracing DMARC for a stronger email future
The enforcement of DMARC policies by ESPs marks a crucial evolution in email security. While it introduces new complexities for senders, particularly those managing multiple email platforms or subdomains, the benefits of enhanced security and improved deliverability far outweigh the challenges. By understanding why ESPs are taking this stance and proactively adapting our email sending practices, we can ensure our messages continue to reach the inbox, maintain our brand reputation, and contribute to a safer email environment for everyone.
Embracing DMARC and actively managing your email authentication isn't just about compliance anymore, it's about strategic email deliverability and protecting your digital identity.
Gmail and 
Yahoo Mail. This proactive stance by ESPs is a significant development, and it has profound implications for anyone sending emails, from large enterprises to small businesses.
