How do I troubleshoot and fix SPF and DMARC settings for email deliverability issues?
Michael Ko
Co-founder & CEO, Suped
Published 16 Jul 2025
Updated 15 Aug 2025
8 min read
Email deliverability can be a complex challenge, and often, the root cause lies in misconfigured Sender Policy Framework (SPF) and Domain-based Message Authentication, Reporting, and Conformance (DMARC) records. These authentication protocols are crucial for ensuring your emails reach their intended inboxes and aren't flagged as spam or rejected outright.
When emails fail to deliver, it's often due to issues with these foundational settings. Without proper SPF and DMARC implementation, along with DKIM (DomainKeys Identified Mail), internet service providers (ISPs) like Google and Yahoo cannot verify that your sending domain is authorized, leading to delivery failures or placement in the spam folder. This can severely impact your communication, marketing efforts, and ultimately, your business.
My goal in this guide is to walk you through the essential steps to troubleshoot and fix common SPF and DMARC issues. By addressing these configurations, you can significantly improve your email deliverability rates and ensure your messages consistently reach their intended recipients. We'll cover everything from initial checks to advanced alignment concerns and practical solutions.
Before diving into troubleshooting, it is essential to have a clear understanding of what SPF and DMARC are and how they interact. SPF (Sender Policy Framework) is a DNS TXT record that lists all authorized mail servers permitted to send emails on behalf of your domain. Receiving mail servers check this record to verify that incoming mail from your domain originates from an authorized server.
DMARC (Domain-based Message Authentication, Reporting, and Conformance) builds upon SPF and DKIM. It tells receiving mail servers how to handle emails that fail SPF or DKIM authentication, such as quarantining them, rejecting them, or simply monitoring the failures. DMARC also provides reporting, giving domain owners visibility into email authentication results and potential abuse.
For DMARC to pass, either SPF or DKIM must achieve identifier alignment. This means the domain used in the SPF 'Mail From' address or the DKIM 'd=' tag must align with the 'From' address domain that the recipient sees. Without this alignment, even if SPF or DKIM pass authentication, DMARC will fail. Proper setup of these records is crucial for email security and preventing spoofing.
One of the most frequent issues I encounter with SPF records is the presence of multiple SPF records for a single domain. DNS allows only one SPF TXT record per domain. Having more than one will invalidate them all, leading to SPF failures. Another common problem is exceeding the 10 DNS lookup limit. Each 'include' mechanism in your SPF record counts as a DNS lookup. If you include too many services, your record will fail SPF checks.
To troubleshoot SPF failures, start by using an online SPF validation tool. This will quickly highlight syntax errors, multiple records, or lookup limit issues. Always ensure that your SPF record includes all IP addresses and third-party services authorized to send emails on your domain's behalf. If you're using a mail provider like Microsoft, make sure their 'include' mechanism is present.
Another specific SPF issue can arise with third-party senders like SendGrid or Mailchimp. Often, these services use their own return-path (Mail From) domain for bounce handling. In such cases, including their SPF in your root domain's SPF record won't help with DMARC SPF alignment, as the Mail From domain is different from your organizational domain. Instead, these services usually recommend DKIM setup for domain authentication, which also satisfies DMARC. Always verify how your specific sending service handles SPF and DKIM for email authentication.
Diagnosing DMARC failures and policy issues
DMARC failures typically occur when an email fails both SPF and DKIM authentication, or when they pass authentication but fail alignment with your 'From' header domain. A common initial setup for DMARC is a 'p=none' policy, which means monitoring only. While this is a good starting point for gathering reports, it doesn't enforce any action on unauthenticated emails. If you notice a high volume of DMARC failures in your aggregate reports, it's time to investigate deeper. You can learn more about how to troubleshoot DMARC failures and their impact on email deliverability.
Alignment issues are a primary cause of DMARC failures. For SPF alignment, the domain in the 'Return-Path' header must match your 'From' header domain (or be a subdomain of it). For DKIM alignment, the domain signed by DKIM ('d=' tag) must match your 'From' header domain. Many third-party email service providers (ESPs) handle the SPF 'Mail From' domain separately, meaning SPF alignment might not pass, even if SPF authentication does. In these cases, ensuring DKIM authentication and alignment is paramount for DMARC compliance. It's important to understand why some emails may fail DMARC checks despite correct SPF and DKIM alignment.
Analyzing your DMARC aggregate reports is the most effective way to identify the source of failures. These XML reports, which can be challenging to read without a dedicated parsing tool, detail which emails passed or failed authentication and why. They also show which sending sources are authenticating correctly (or not). Reviewing these reports helps you determine if unauthorized senders are using your domain or if legitimate emails are failing due to misconfiguration. The Google Workspace Admin Help provides guidance on troubleshooting DMARC issues.
DMARC policy explained
p=none: This is the monitoring policy. It tells recipients to take no action on failed emails but to send DMARC reports to your specified address. Ideal for initial deployment to gather data without impacting deliverability. You can refer to simple DMARC examples for more information.
p=quarantine: Instructs recipients to place failed emails into the spam or junk folder. Use this policy once you are confident that legitimate emails are passing DMARC.
p=reject: The strictest policy, telling recipients to refuse failed emails entirely. This should only be implemented after extensive monitoring and ensuring all legitimate sending sources are fully compliant.
Implementing fixes and best practices
Once you've identified the specific SPF and DMARC issues, it's time to implement fixes. For SPF, consolidate all authorized sending sources into a single TXT record. If you have multiple services, ensure they are listed correctly using 'include' mechanisms. Remember to stay within the 10 DNS lookup limit. If you're struggling with this, consider using an SPF flattening service to combine multiple includes into one. Also, confirm that your SPF record accurately reflects all your current email sending infrastructure.
For DMARC, focus on achieving SPF or DKIM alignment for all legitimate email streams. If a third-party service does not allow for SPF alignment with your 'From' domain, ensure their DKIM authentication is correctly set up. Many ESPs provide specific instructions for DKIM record creation. Once DKIM is correctly implemented and aligned, it will satisfy the DMARC requirement even if SPF alignment cannot be achieved. You can also refer to the Duocircle DMARC TempError guide for more insights into fixing common email authentication issues.
After making changes to your DNS records, allow sufficient time for DNS propagation. This can take anywhere from a few minutes to several hours, depending on your DNS provider. Continuously monitor your DMARC reports after making changes to ensure they have the desired effect and that no new issues arise. This iterative process of monitoring, analyzing, and adjusting is key to maintaining optimal email deliverability and protecting your domain from unauthorized use. For a comprehensive overview, see how to set up and troubleshoot SPF, DKIM, and DMARC.
Common problems
Multiple SPF records: Only one SPF TXT record is allowed per domain. Multiple records will lead to validation failures and impact deliverability.
DNS lookup limit (10): Too many 'include' mechanisms in your SPF record can exceed the limit, causing authentication failures.
DMARC alignment failure: Even if SPF or DKIM pass, if the domains in the 'Mail From'/'d=' tag don't align with the 'From' header, DMARC will fail.
Effective solutions
Consolidate SPF records: Combine all authorized senders into a single, valid SPF TXT record.
Optimize lookups: Use 'a', 'mx', and 'ip4' mechanisms where appropriate and consider SPF flattening services.
Prioritize DKIM for DMARC: Ensure strong DKIM authentication and alignment for services that do not support SPF alignment.
Views from the trenches
Best practices
Always use a DMARC monitoring service to receive aggregate reports and identify all sending sources.
Start with a DMARC policy of p=none (monitoring) to gather data before moving to quarantine or reject.
Ensure all third-party email service providers (ESPs) are correctly configured with DKIM and SPF.
Regularly review your DNS records for SPF, DKIM, and DMARC to account for changes in your sending infrastructure.
Common pitfalls
Having multiple SPF records for a single domain, which invalidates them all.
Exceeding the 10 DNS lookup limit in your SPF record, leading to authentication failures.
Not understanding that third-party ESPs may handle SPF alignment differently, requiring strong DKIM.
Implementing a DMARC policy of p=reject too early, causing legitimate emails to be blocked.
Expert tips
If SPF alignment is difficult with a third-party sender, prioritize DKIM alignment as DMARC only requires one to pass.
DMARC is not just a DNS record change; it's a deployment that requires ongoing monitoring and analysis.
Consider the impact of email forwarding on DKIM authentication and DMARC pass rates, as forwarding can break DKIM.
Use ARC (Authenticated Received Chain) with more aggressive DMARC policies to better handle indirect mail flows.
Expert view
Expert from Email Geeks says that when deploying DMARC across an organization, it is a significant undertaking that can take at least six months to a year to fully implement, especially when aiming for a reject policy. Professional tools are available to help with this process.
2020-09-04 - Email Geeks
Marketer view
Marketer from Email Geeks says that DMARC monitoring mode (p=none) is crucial for identifying authentication issues, and it is generally safe to implement because there is no risk of legitimate emails being quarantined or rejected.
2020-09-05 - Email Geeks
Final thoughts on email authentication
Troubleshooting and fixing SPF and DMARC settings are critical steps for anyone looking to optimize their email deliverability. These authentication protocols not only help ensure your legitimate emails reach the inbox but also protect your domain from being used for spoofing and phishing attacks.
By systematically checking your DNS records for SPF syntax errors, multiple records, and lookup limits, and by carefully analyzing your DMARC reports for alignment failures, you can pinpoint and resolve most common issues. Remember that implementing DMARC, especially moving to a more restrictive policy, is a journey that requires careful monitoring and adjustment.
Investing time in properly configuring and maintaining your SPF and DMARC records will pay off in higher inbox placement rates, improved sender reputation, and enhanced security for your domain and your recipients. Consistent monitoring and proactive adjustments are key to long-term email deliverability success.
Google and 
Yahoo cannot verify that your sending domain is authorized, leading to delivery failures or placement in the spam folder. This can severely impact your communication, marketing efforts, and ultimately, your business.
Microsoft, make sure their 'include' mechanism is present.
SendGrid or 
Mailchimp. Often, these services use their own return-path (Mail From) domain for bounce handling. In such cases, including their SPF in your root domain's SPF record won't help with DMARC SPF alignment, as the Mail From domain is different from your organizational domain. Instead, these services usually recommend DKIM setup for domain authentication, which also satisfies DMARC. Always verify how your specific sending service handles SPF and DKIM for email authentication.
