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Mastering SPF for Subdomains: Enhancing Email Security and Deliverability

Published on
May 28, 2025

When it comes to email security, a few things are as critical or misunderstood as SPF (Sender Policy Framework) for subdomains. If you’re sending emails from addresses like marketing.yourdomain.com or support.yourdomain.com, you might wonder: “Do I really need SPF for these?” The short answer is yes, and skipping it could leave your emails vulnerable to spoofing, spam filters, or outright rejection.

Let’s break it down and make SPF your email’s best friend.

What Does an SPF Record Look Like?

An SPF record is a text-based DNS record that specifies the authorized mail servers for a domain or subdomain. It acts as a security checkpoint, ensuring only trusted senders can use your domain’s name in emails. Here’s what it looks like:

  • Structure: It starts with v=spf1 (the SPF version), followed by mechanisms like include (to reference another domain’s SPF policy) or ip4 (to specify an IP address), and ends with an all mechanism that defines what happens to unauthorized senders.

Example:

v=spf1 include:spf.domain.com include:spf.xyz.net -all
  • This record says: “Emails from my domain can come from servers listed in spf.domain.com and spf.xyz.net. Reject anything else (-all).”

Simple yet powerful, an SPF record is your first line of defense against email spoofing.

Do I Need SPF for Subdomains?

Yes, if your subdomains send emails. Subdomains—like news.yourdomain.com or support.yourdomain.com—do not automatically inherit the SPF record from your root domain (yourdomain.com). If these subdomains are used for sending emails (e.g., newsletters, customer support), they need their own SPF records. Here’s why:

  • Deliverability: Without an SPF record, emails from your subdomains may be flagged as spam or rejected by receiving servers, hurting your email deliverability.
  • Security: Unprotected subdomains are prime targets for spoofers, who can send phishing emails under your brand’s name, damaging your reputation.

Skipping SPF for subdomains isn’t just a technical oversight—it’s a risk. With phishing attempts on the rise in 2025, securing every email-sending subdomain is more critical than ever.

How Does SPF Work with Subdomains?

SPF operates independently for each subdomain. Here’s the process:

  1. Email Sent: An email is sent from hello@marketing.yourdomain.com.
  2. DNS Check: The recipient’s server looks up the SPF record for marketing.yourdomain.com (not yourdomain.com).
  3. Validation: It checks if the sender’s IP is listed in the SPF record. If it matches, the email passes. If not, it’s flagged or rejected based on your all setting.

This ensures only your authorized services can send emails from your subdomains, keeping imposters at bay. It’s a straightforward yet essential mechanism for maintaining trust in your email communications.

Creating an SPF Record for Your Subdomains

Setting up SPF for subdomains is straightforward but requires precision. Here’s how to do it:

  1. Identify Email-Sending Subdomains: List all subdomains that send emails (e.g., news.yourdomain.com, support.yourdomain.com).
  2. Determine Email Providers: Note the services sending emails for each subdomain (e.g., Google Workspace, Mailchimp, SendGrid).
  3. Generate the Record: Create a record manually or simplify the process with Palisade’s AI-Assisted Workflow. Examples:
  4. Check for Errors: SPF records have a 10-DNS-lookup limit. Exceeding it can render your record invalid—a common mistake Palisade’s tools help you avoid.

Pro Tip: Use ~all (soft fail) during testing to monitor results without blocking legitimate emails, then switch to -all (hard fail) for full protection.

Publishing Your Subdomain’s SPF Record

Once your SPF record is ready, it’s time to publish it in your DNS:

  1. Access Your DNS Console: Log into your provider (e.g., GoDaddy, Cloudflare, Namecheap).
  2. Add a TXT Record:
    • Host/Name: Enter the subdomain (e.g., news for news.yourdomain.com).
    • Type: Select “TXT.”
    • Value: Paste your SPF record (e.g., v=spf1 include:servers.mcsv.net ~all).
    • TTL: Set to “Auto” or 1 hour.
  3. Save and Wait: DNS changes can take up to 48 hours to propagate. Use a tool like WhatsMyDNS to verify.

Watch Out: A frequent error is entering the full subdomain (news.yourdomain.com) instead of just news in the host field. Keep it concise to avoid issues.

Simplify Your SPF Setup with Palisade’s AI-Assisted Workflow

Managing SPF across multiple subdomains doesn’t have to be a hassle. Palisade’s AI-Assisted Workflow streamlines the process:

  • Quick Setup: Automatically generates accurate SPF records tailored to your email services.
  • Error Prevention: Ensures compliance with SPF limits and best practices.
  • Ongoing Support: Monitors and updates your records as your needs evolve.

With Palisade, you can secure your subdomains efficiently, leaving more time to focus on your business.

Take Control of Your Subdomains Today

SPF for subdomains is your ticket to secure, deliverable emails in 2025. By setting up individual records, publishing them correctly, and leveraging tools like Palisade’s AI-Assisted Workflow, you’ll protect your brand and keep your messages flowing. Don’t let spoofers or spam filters derail you—act now.

Ready to lock it down? Sign up with Palisade and simplify your SPF setup today.

Published on
June 2, 2025
Author
Samuel Chenard - Founder & CEO
Email Performance Score
Improve results with AI- no technical skills required

Mastering SPF for Subdomains: Enhancing Email Security and Deliverability

Published on
June 2, 2025
Contributors
Dominic Landry
Email security specialist
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When it comes to email security, a few things are as critical or misunderstood as SPF (Sender Policy Framework) for subdomains. If you’re sending emails from addresses like marketing.yourdomain.com or support.yourdomain.com, you might wonder: “Do I really need SPF for these?” The short answer is yes, and skipping it could leave your emails vulnerable to spoofing, spam filters, or outright rejection.

Let’s break it down and make SPF your email’s best friend.

What Does an SPF Record Look Like?

An SPF record is a text-based DNS record that specifies the authorized mail servers for a domain or subdomain. It acts as a security checkpoint, ensuring only trusted senders can use your domain’s name in emails. Here’s what it looks like:

  • Structure: It starts with v=spf1 (the SPF version), followed by mechanisms like include (to reference another domain’s SPF policy) or ip4 (to specify an IP address), and ends with an all mechanism that defines what happens to unauthorized senders.

Example:

v=spf1 include:spf.domain.com include:spf.xyz.net -all
  • This record says: “Emails from my domain can come from servers listed in spf.domain.com and spf.xyz.net. Reject anything else (-all).”

Simple yet powerful, an SPF record is your first line of defense against email spoofing.

Do I Need SPF for Subdomains?

Yes, if your subdomains send emails. Subdomains—like news.yourdomain.com or support.yourdomain.com—do not automatically inherit the SPF record from your root domain (yourdomain.com). If these subdomains are used for sending emails (e.g., newsletters, customer support), they need their own SPF records. Here’s why:

  • Deliverability: Without an SPF record, emails from your subdomains may be flagged as spam or rejected by receiving servers, hurting your email deliverability.
  • Security: Unprotected subdomains are prime targets for spoofers, who can send phishing emails under your brand’s name, damaging your reputation.

Skipping SPF for subdomains isn’t just a technical oversight—it’s a risk. With phishing attempts on the rise in 2025, securing every email-sending subdomain is more critical than ever.

How Does SPF Work with Subdomains?

SPF operates independently for each subdomain. Here’s the process:

  1. Email Sent: An email is sent from hello@marketing.yourdomain.com.
  2. DNS Check: The recipient’s server looks up the SPF record for marketing.yourdomain.com (not yourdomain.com).
  3. Validation: It checks if the sender’s IP is listed in the SPF record. If it matches, the email passes. If not, it’s flagged or rejected based on your all setting.

This ensures only your authorized services can send emails from your subdomains, keeping imposters at bay. It’s a straightforward yet essential mechanism for maintaining trust in your email communications.

Creating an SPF Record for Your Subdomains

Setting up SPF for subdomains is straightforward but requires precision. Here’s how to do it:

  1. Identify Email-Sending Subdomains: List all subdomains that send emails (e.g., news.yourdomain.com, support.yourdomain.com).
  2. Determine Email Providers: Note the services sending emails for each subdomain (e.g., Google Workspace, Mailchimp, SendGrid).
  3. Generate the Record: Create a record manually or simplify the process with Palisade’s AI-Assisted Workflow. Examples:
  4. Check for Errors: SPF records have a 10-DNS-lookup limit. Exceeding it can render your record invalid—a common mistake Palisade’s tools help you avoid.

Pro Tip: Use ~all (soft fail) during testing to monitor results without blocking legitimate emails, then switch to -all (hard fail) for full protection.

Publishing Your Subdomain’s SPF Record

Once your SPF record is ready, it’s time to publish it in your DNS:

  1. Access Your DNS Console: Log into your provider (e.g., GoDaddy, Cloudflare, Namecheap).
  2. Add a TXT Record:
    • Host/Name: Enter the subdomain (e.g., news for news.yourdomain.com).
    • Type: Select “TXT.”
    • Value: Paste your SPF record (e.g., v=spf1 include:servers.mcsv.net ~all).
    • TTL: Set to “Auto” or 1 hour.
  3. Save and Wait: DNS changes can take up to 48 hours to propagate. Use a tool like WhatsMyDNS to verify.

Watch Out: A frequent error is entering the full subdomain (news.yourdomain.com) instead of just news in the host field. Keep it concise to avoid issues.

Simplify Your SPF Setup with Palisade’s AI-Assisted Workflow

Managing SPF across multiple subdomains doesn’t have to be a hassle. Palisade’s AI-Assisted Workflow streamlines the process:

  • Quick Setup: Automatically generates accurate SPF records tailored to your email services.
  • Error Prevention: Ensures compliance with SPF limits and best practices.
  • Ongoing Support: Monitors and updates your records as your needs evolve.

With Palisade, you can secure your subdomains efficiently, leaving more time to focus on your business.

Take Control of Your Subdomains Today

SPF for subdomains is your ticket to secure, deliverable emails in 2025. By setting up individual records, publishing them correctly, and leveraging tools like Palisade’s AI-Assisted Workflow, you’ll protect your brand and keep your messages flowing. Don’t let spoofers or spam filters derail you—act now.

Ready to lock it down? Sign up with Palisade and simplify your SPF setup today.