When setting up DMARC for your domain, you'll encounter various tags that control how email receivers handle messages. One tag that often causes confusion is the sp tag, which stands for "subdomain policy." Many domain owners wonder if this tag is a mandatory component of a valid DMARC record.
The short answer is no, the sp tag is not mandatory in a DMARC record. While it plays a crucial role in defining policies for subdomains, a DMARC record can be perfectly valid and functional without it. Understanding when and why to use sp is key to effective email security and deliverability.
Email authentication protocols like DMARC, SPF, and DKIM are fundamental to protecting your domain from phishing and spoofing. Ensuring your DMARC record is correctly configured, whether it includes the sp tag or not, is essential for maintaining trust and ensuring your legitimate emails reach their intended recipients.
Understanding the 'sp' tag
The sp tag in a DMARC record is specifically designed to apply a DMARC policy to all subdomains of the organizational domain where the DMARC record is published. This is distinct from the p tag, which sets the policy for the organizational domain itself. Without an explicit sp tag, subdomains will inherit the policy specified by the p tag of the main domain.
For example, if your main domain is example.com, and you have subdomains like marketing.example.com or support.example.com, the sp tag would dictate their DMARC policy. This allows for granular control over different parts of your email infrastructure. You can find more details on how this works on duocircle.com, an authoritative resource on the topic.
The hierarchy of DMARC policies
Understanding how the sp tag affects policies for subdomains is critical. If present, it overrides the p tag for subdomains, giving you more flexibility. If sp is omitted, subdomains simply follow the main p policy. This hierarchy is a core concept in DMARC implementation.
For domains with complex email setups involving numerous subdomains, the sp tag becomes a powerful tool. It allows you to tailor your DMARC enforcement based on the specific usage of each subdomain, which might range from marketing emails to internal communications. Learn more about how the DMARC sp tag affects subdomain policies for a deeper dive.
When the 'sp' tag is (and isn't) needed
As established, the sp tag is not universally required. Many organizations can operate effectively with a DMARC record that only includes the p tag, letting subdomains inherit that policy. This simplifies DMARC management, especially for domains with a straightforward subdomain structure or those that don't send email from subdomains. For instance, if you only send email from your main domain, yourdomain.com, and not from news.yourdomain.com, then an explicit sp might not be necessary.
However, the sp tag becomes valuable when you need to apply a different policy to your subdomains than to your main domain. This is particularly relevant if your subdomains are used for different purposes or managed by different entities. For example, you might want to enforce a p=reject policy on your main domain for maximum protection, but keep subdomains at sp=none while you gather DMARC reports and gradually move towards enforcement. Learn more about the default value for the DMARC 'p' tag to understand its baseline behavior.
Ultimately, the decision to include the sp tag depends on your organization's specific needs and subdomain usage. There is no one-size-fits-all answer, so evaluate your email infrastructure carefully. For instance, if your DMARC policy is set to p=none and sp=none, the pct tag's behavior for percentage enforcement can be quite different. You can read more on how the pct tag in DMARC works.
Implications of not using 'sp'
If you choose to omit the sp tag from your DMARC record, your subdomains will automatically inherit the policy defined by the p tag for your organizational domain. For example, if your DMARC record specifies p=quarantine, then all unauthenticated emails from your subdomains will also be quarantined.
This default inheritance is often sufficient, especially when you are starting with DMARC implementation at p=none to monitor your email traffic. However, it can become a security vulnerability or lead to deliverability issues if you are not fully aware of all your sending sources across subdomains. If a subdomain is actively used for email, but you haven't properly configured SPF or DKIM for it, emails from that subdomain might fail DMARC authentication and be rejected if your main policy is p=reject.
This is why ongoing DMARC monitoring is crucial. By regularly reviewing your DMARC reports, you can identify legitimate email sources that are failing authentication and take corrective actions. Without monitoring, you might unknowingly block legitimate emails or allow malicious ones to slip through if your inherited subdomain policy isn't robust enough. Suped offers a comprehensive DMARC monitoring platform that provides actionable insights to prevent these issues.
Best practices for DMARC policies and subdomains
To ensure robust email security and deliverability, it's wise to adopt best practices for managing your DMARC policies, whether you use the sp tag or not. Start with a relaxed policy like p=none and closely analyze your DMARC reports. This allows you to identify all legitimate email senders for your main domain and subdomains before moving to more restrictive policies. You can find simple DMARC examples to guide your initial setup.
Monitor reports: Use a DMARC reporting tool like Suped to gain visibility into your email ecosystem. Suped provides AI-powered recommendations, real-time alerts, and a unified platform for DMARC, SPF, and DKIM monitoring.
Gradual enforcement: Move from none to quarantine, then to reject as you gain confidence in your DMARC alignment. This gradual approach helps safely transition your DMARC policy.
Consider 'sp' for complex setups: If you have many subdomains with distinct email sending patterns, explicitly setting the sp tag is a powerful way to manage their policies individually.
Remember, the goal of DMARC is to prevent email impersonation and protect your brand's reputation. Whether you choose to use the sp tag or rely on policy inheritance, consistent monitoring and thoughtful policy adjustments are key. Tools like Suped provide the visibility and guidance needed to navigate DMARC with confidence, offering even a generous free plan to get started.
Ensuring robust email security
In conclusion, the 'sp' tag is not a mandatory element of a DMARC record. Its inclusion depends on your specific needs for managing subdomain policies. If omitted, subdomains will inherit the 'p' tag's policy. For simple setups, this inheritance might be sufficient. However, for organizations with diverse email sending practices across multiple subdomains, leveraging the 'sp' tag offers invaluable granular control. The most important aspect is to have a DMARC record in place, monitor its performance, and gradually move towards stronger enforcement to protect your domain from abuse. Utilizing a robust DMARC monitoring solution like Suped can simplify this process and help you achieve optimal email security.
