How to set up DMARC with multiple email senders for the same domain?
Matthew Whittaker
Co-founder & CTO, Suped
Published 17 Jun 2025
Updated 19 Aug 2025
8 min read
Many organizations today rely on multiple email sending services for different purposes. You might use one provider for marketing campaigns, another for transactional emails like order confirmations, and perhaps a third for customer support communications, all originating from the same primary domain. This setup, while efficient for operations, often raises questions about how to properly implement DMARC without disrupting email delivery.
The core challenge lies in ensuring that every email sent from your domain, regardless of the sending service, correctly passes DMARC (Domain-based Message Authentication, Reporting, and Conformance) authentication checks. DMARC builds upon SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail), requiring at least one of these to align with the domain in the 'From' header.
The good news is that setting up DMARC with multiple email senders for the same domain is not only possible but also a critical step in enhancing your email security and deliverability. It helps prevent malicious actors from spoofing your domain, protecting your recipients and your brand reputation.
I'll guide you through the process, emphasizing a phased approach that starts with monitoring to identify all legitimate sending sources before moving towards enforcement policies. This methodical strategy minimizes the risk of inadvertently blocking legitimate emails.
Setting the foundation: SPF and DKIM for multiple senders
Before you can even think about DMARC, you need to ensure that SPF and DKIM are properly configured for every service that sends email on behalf of your domain. These are the foundational email authentication protocols that DMARC leverages. SPF authorizes sending IP addresses, while DKIM provides a digital signature for your emails.
For SPF, remember that you can only have one SPF record per domain. This single TXT record in your DNS must include all legitimate email sending services. If you have multiple SPF records, you'll need to merge them into a single record using the include mechanism. Each service will provide its own include statement.
DKIM records are typically unique to each sending service. They will provide you with specific DNS entries, often CNAME records, that contain a public key. This key allows receiving mail servers to verify the authenticity of your emails. It's crucial that each email service provider (ESP) you use has its DKIM correctly set up and enabled for your domain. This ensures that the messages they send on your behalf are signed and verifiable.
Consolidating SPF records
If you have multiple SPF records (or multiple service providers that each want to add their own), you must combine them into a single record. The include mechanism allows you to authorize multiple external senders. Remember to keep the total number of DNS lookups under the SPF 10-lookup limit.
Achieving DMARC alignment means that either the SPF-authenticated domain or the DKIM-signed domain (or both) must match your email's 'From' header domain. For third-party senders, this often means ensuring they send emails using a subdomain of your primary domain, or that their DKIM signature is on your primary domain.
Crafting your DMARC record for a shared domain
A common misconception is that you need multiple DMARC records for multiple senders. This is incorrect. A domain can only have one DMARC record for the root domain or individual subdomains. This single TXT record is published at _dmarc.yourdomain.com and defines the policy for all emails originating from your domain and its subdomains, unless a specific subdomain has its own DMARC record.
Your DMARC record is composed of various tags, but the most important ones for our discussion are p (policy), rua (aggregate reports), and ruf (forensic reports). When you are first setting up, you should always begin with a policy of p=none. This policy acts as a monitoring-only mode, providing valuable insight into your email flows without impacting deliverability. For reporting, you can list multiple email addresses in the rua tag, separating them with commas and prepending each with mailto:, as explained by Google Workspace Admin Help.
DMARC alignment is the cornerstone of its effectiveness. It checks if the domain authenticated by SPF or DKIM matches the domain in the 'From' header seen by the recipient. When you use multiple senders, each sender's configuration must ensure this alignment. For example, if your marketing ESP sends emails as marketing@yourdomain.com, their SPF or DKIM authentication must pass for yourdomain.com (or an aligned subdomain).
Email address(es) for forensic reports (less common).
fo
Failure reporting options. fo=1 sends reports if any underlying authentication fails.
adkim
DKIM alignment mode (strict s or relaxed r).
aspf
SPF alignment mode (strict s or relaxed r).
pct
Percentage of emails to apply policy to (0-100).
Monitoring and evolving your DMARC policy
Once your DMARC record with p=none is published, the real work begins. You'll start receiving DMARC aggregate reports (RUAs) from mailbox providers like Microsoft and Yahoo. These XML reports, while complex, provide a comprehensive overview of all email traffic claiming to be from your domain, indicating which sources are passing or failing SPF and DKIM authentication and DMARC alignment. You can find more details in the DMARC.org wiki.
Your primary goal in the monitoring phase is to identify every legitimate email sending source that is not currently passing DMARC. This is often referred to as "finding your holes". For each failing legitimate source, you need to work with that email service provider to ensure they are correctly authenticating and aligning emails with your domain. This might involve setting up specific DKIM keys or ensuring their IP addresses are included in your SPF record. You can use DMARC monitoring tools to help parse these reports.
Once you are confident that all your legitimate email streams are passing DMARC authentication, you can gradually move to a more enforced policy. The progression is typically from p=none to p=quarantine (mail that fails DMARC is sent to the spam folder) and finally to p=reject (mail that fails DMARC is blocked entirely). This phased approach, as detailed in our guide on safely transitioning DMARC policy, is critical to avoid accidental disruptions.
The initial phase
Safety: No impact on email deliverability, as failing emails are not blocked.
Visibility: Provides comprehensive reports on all sending sources, both authorized and unauthorized.
Identification: Helps to identify any legitimate email streams that might be misconfigured or lacking proper authentication.
The enforcement phases
Security: Actively prevents email spoofing and phishing attacks by unauthorized senders.
Risk: Incorrect configuration can lead to legitimate emails being quarantined or rejected.
Preparation: Requires thorough analysis of DMARC reports and ensuring all legitimate senders are aligned before deployment.
Gradual policy enforcement is key
Moving to a p=quarantine or p=reject policy without proper testing and validation can lead to significant deliverability issues for your legitimate emails. Always monitor reports closely and resolve any failures before increasing your policy enforcement.
Best practices for ongoing DMARC management
To better manage DMARC with multiple senders, consider using subdomains for different types of email traffic. For instance, you could use marketing.yourdomain.com for campaigns and transactional.yourdomain.com for automated messages. This allows you to apply different DMARC policies to each subdomain if needed, offering more granular control and easier troubleshooting. Our article on DMARC records for subdomains provides more detail.
Maintaining a comprehensive inventory of all your email sending services, including their SPF include statements and DKIM selectors, is crucial for effective DMARC management. Regular audits of these configurations, especially when onboarding new services or deprecating old ones, will help prevent authentication failures. This proactive approach helps maintain a healthy sender reputation and avoid being added to email blocklists (or blacklists).
Finally, always ensure that any third-party email sending service you use provides robust support for SPF and DKIM authentication. Most reputable providers offer clear instructions for setting up custom domain authentication, which is essential for achieving DMARC alignment. Prioritize providers that make this process straightforward, as it will significantly ease your DMARC implementation and maintenance efforts.
The benefits of DMARC
Enhanced Security: Protects your domain from spoofing and phishing attacks by preventing unauthorized use of your brand in email.
Improved Deliverability: Signals to mailbox providers that your emails are legitimate, leading to better inbox placement and reduced chances of hitting spam folders. Check out our best practices for authentication.
Visibility & Control: DMARC reports provide invaluable insights into your email ecosystem, helping you identify and rectify authentication issues.
Views from the trenches
Best practices
Always begin with a DMARC policy of p=none to gather comprehensive reports without affecting delivery.
Maintain a detailed inventory of all email sending services and their respective authentication setups.
Regularly review DMARC aggregate reports to identify new or misconfigured email sending sources.
Consider using specific subdomains for different types of email (e.g., marketing, transactional) to streamline management.
Common pitfalls
Deploying a p=quarantine or p=reject policy too quickly, leading to legitimate emails being blocked.
Failing to consolidate multiple SPF records into a single, comprehensive SPF record.
Not configuring SPF and DKIM for every single email sending service used by your domain.
Ignoring DMARC reports, which contain critical information about your email authentication status.
Expert tips
Use a DMARC reporting service to simplify the analysis of complex XML reports.
Set a sp=none (subdomain policy of none) initially to ensure full visibility across all subdomains.
Regularly audit your DNS records to confirm they align with your DMARC strategy.
Communicate DMARC requirements clearly with all departments and third-party vendors who send email.
Expert view
Expert from Email Geeks says: Start with a 'none' policy to identify issues, then gradually move to 'quarantine' and 'reject' after addressing all unauthenticated legitimate email flows.
2019-09-12 - Email Geeks
Expert view
Expert from Email Geeks says: Using a p=none policy, along with sp=none for subdomains, allows for reporting mode without immediate enforcement.
2019-09-12 - Email Geeks
Securing your domain, one sender at a time
Setting up DMARC with multiple email senders for the same domain might seem daunting at first, but it's a manageable and highly beneficial process. By ensuring proper SPF and DKIM configurations for each service, publishing a single DMARC record, and taking a phased approach to policy enforcement, you can significantly strengthen your email security posture.
The key is diligence in monitoring your DMARC reports and systematically addressing any authentication failures. This continuous process ensures that all your legitimate emails reach their intended inboxes while blocking malicious attempts to use your domain for spam or phishing.
Embracing DMARC provides greater control over your email ecosystem, improves your sender reputation, and ultimately enhances trust in your brand. It's an essential layer of protection in today's digital landscape.
Microsoft and 
Yahoo. These XML reports, while complex, provide a comprehensive overview of all email traffic claiming to be from your domain, indicating which sources are passing or failing SPF and DKIM authentication and DMARC alignment. You can find more details in the DMARC.org wiki.
