Is Your DNS SPF Record Costing You Email ROI? Act Now

Email is still the backbone of business communication, but it’s also the most targeted channel for cyberattacks. Spoofed domains, phishing campaigns, and spam don’t just hurt your reputation; they can block legitimate emails from ever reaching customers’ inboxes. The most common cause? Weak or missing email authentication.

For businesses that rely on email marketing, internal communication, or transactional notifications, even one spoofing incident or deliverability drop can impact revenue, compliance, and brand trust. Implementing Sender Policy Framework (SPF) records is a critical first step in closing that gap.

Think of SPF as a DNS‑level security gate for your domain. It ensures that only approved senders — your internal servers and trusted email partners like Mailchimp or Gmail — can deliver emails on your behalf. Any sender not on your list is rejected, protecting you against impersonation and phishing.

SPF is also part of the broader family of domain-based message authentication, reporting, and conformance (DMARC) tools that give businesses complete visibility and control over their outbound email authentication.

This guide walks through how SPF works, why it matters for deliverability and security, the pitfalls to avoid, and how to combine SPF with DKIM and DMARC for full protection.

How does an SPF record work to protect your domain?

SPF operates as a checkpoint for every incoming email claiming to come from your domain:

• The sending server initiates an email using your domain in the SMTP return-path.
• The receiving mail server queries your domain’s DNS to find the SPF record.
• The server compares the sender’s IP address to the authorized IPs and hosts in your record.

Result:

• Match → Email is accepted for delivery and can pass to DMARC for policy enforcement.
• No match → Email is rejected or flagged as spam, protecting your recipients.

For businesses running multi‑vendor or global email infrastructure, this step prevents unauthorized servers — including those used in phishing attacks — from ever reaching inboxes and reduces false positives that can hurt marketing ROI.

What is the correct SPF record syntax, and how do you use it?

SPF records are text (TXT) files that include the SPF version and mechanisms that note the authorized sender's host names and IP addresses.

An SPF record example would look like this:

The "v=spf1" part of the text denotes that this is an SPF record, while the “a” tells the server that it needs to match the record with the following domain. MX is the mail server or host, e.g., Google, Mailchimp, or Microsoft. Every domain authorized to send emails must have an "include" statement that includes the domain clearly noted. “All” authorizes every IP address for the domain to send emails.

Why are SPF records critical for email security and deliverability?

It’s still possible to send emails from a business email address without having SPF records in place. However, with these enabled, companies improve their email security, both for themselves and those receiving their emails.

Prevent email spoofing 

Email spoofing is a specific type of cybercrime in which criminals fraudulently send emails with a fake email address that looks as though it’s a real business. The goal is to get the recipient to click on links within the email, thinking it’s a trusted source. Instead, those links take them to a site containing malware or where they input login information. From there, cyber criminals can gain access to their private information.

With SPF records in place, it’s much harder for criminals to do this. Since the SPF record is being matched by both the sending and receiving servers by IP address, criminals aren’t able to impersonate the business simply by email alone. Instead, their emails will bounce as they won’t be an authorized sender via an SPF record. 

Improve deliverability 

When a business uses an SPF record, it’s letting mail servers know they have an approved list of email providers. This makes them a more trustworthy source, meaning emails are less likely to be marked as spam or bounce when sent to a recipient’s email inbox. 

Deliverability statistics are essential for businesses, particularly in marketing. Poor deliverability means that a business is spending money on sending emails that aren’t going to people’s inboxes, resulting in a low return on investment (ROI). High deliverability can also help improve sales and build trust with an audience via email marketing campaigns.

Protect business reputation 

Sending emails to someone is one of the most personal forms of communication a business can make. Keeping that trust is essential for maintaining a good reputation and continuing to grow the organization. With SPF records, recipients know that the email they’re receiving is genuinely from the company and not someone impersonating them.

How do SPF records affect sender reputation and ROI?

SPF records aren’t just a technical checkbox — they have a direct impact on how mailbox providers perceive your domain and whether your emails actually land in inboxes. Strong authentication through SPF contributes to higher sender reputation, which directly affects marketing ROI and operational reliability.

Why sender reputation matters for business outcomes

Mailbox providers like Gmail, Outlook, and Yahoo constantly evaluate sending domains to determine whether incoming mail is legitimate. Even one misstep in authentication can lower your reputation, leading to:

• More emails landing in spam folders: Poorly authenticated domains trigger filters even if your content is clean.
• Lower open and click rates: If your campaigns are hidden in spam, your engagement metrics fall quickly.
• Wasted marketing spend: Every undelivered email represents lost ROI, especially for paid campaigns or lead-nurture sequences.

Recent industry reports show that nearly 16–20% of business emails never reach the inbox due to reputation issues, often linked to missing or misconfigured authentication.

How SPF directly impacts deliverability and ROI

A properly configured SPF record gives mailbox providers a verifiable signal that your sending servers are authorized, which supports better inbox placement over time. This doesn’t act in isolation — SPF works best when combined with DKIM and DMARC — but it is the first step in building domain trust and protecting campaign ROI.

Think of SPF as the baseline for a sender reputation strategy: without it, even high‑quality campaigns may underperform simply because they fail to clear authentication checks.

What are the limitations of SPF records you should be aware of?

While implementing SPF records has plenty of benefits, there are also some noteworthy limitations to remember.

• No message encryption. Unlike more secure means of email, SPF records don’t offer end-to-end encryption on emails. This makes it possible for sensitive information to be passed to the wrong recipient without other security measures in place.
• Forwarding emails breaks the record. If emails are forwarded to another recipient, that user’s email return path becomes the new start of the chain, and the original SPF records are not passed through. This can result in failed authentication, as the records no longer match.
• SPF alone isn't protection from cyber crime. SPF records are a great solution to implement but should always be used with additional cybersecurity measures for the highest level of protection.
• There are lookup limitations. SPF records often limit mail servers to 10 DNS lookups at a time to prevent denial of service (DoS) attacks. This is usually not an issue for simple DNS records, but more complex ones can sometimes run into technical issues.

What are the most common SPF record mistakes, and how do you fix them?

Misconfigurations in SPF are a top reason for deliverability drops, false positives in spam filtering, and failed phishing defenses. The good news is that most problems are predictable, testable, and reversible with a clear playbook. Use the patterns below to diagnose issues quickly and apply fixes with confidence.

Do you have more than one SPF record on the same domain?

Only one SPF TXT record is valid per domain. If a domain publishes two or more SPF TXT records, many receivers treat the result as a permission error and skip SPF entirely.

How to fix it, step by step:

• Before you merge anything, take an inventory of every service that sends on your behalf and confirm which includes are required. Then consolidate into a single record.
• Gather all existing SPF fragments for your domain and subdomains and list the mechanisms you actually use.
• Remove duplicates and obsolete vendors. Keep only the active IPs and include.
• Merge into one record, preserving version at the start and qualifier at the end.
• Publish and test with a seed list and an authentication checker in a staging window before rollout.
  

Are you exceeding the 10 DNS lookup limit?

SPF allows a maximum of 10 DNS lookups during evaluation. Mechanisms that trigger lookups include include, a, mx, ptr (discouraged), and exists. Being chained across multiple providers can push you over the limit and affect performance results.

How to fix it, step by step:

• Start by measuring your effective lookup count and then reduce it without losing coverage.
• Replace broad mechanisms with explicit IP ranges where feasible, for example swap mx or a for ip4 and ip6 entries published by your provider.
• Eliminate nested or redundant include chains. Prefer a single provider include that already aggregates its sending networks.
• Ask vendors whether they offer a “subinclude” built for customers who must keep lookup counts low.
• If you use SPF flattening, automate it. Manual flattening goes stale when providers rotate IPs.

Are you using the wrong policy qualifier at the end?

The terminal mechanism determines how receivers should treat senders not listed in your record. Common choices are ~all (softfail) and -all (fail). Staying on ~all forever weakens enforcement, while jumping to -all too soon can break legitimate traffic.

How to fix it, step by step:

• Treat policy as a phased control, not a one-time switch.
• Start with ~all during discovery, while you confirm all authorized senders.
• Monitor bounces and authentication results to identify stragglers such as forgotten SaaS tools or regional IPs.
• Move to -all once logs show that only unauthorized sources are being blocked.
• Reassess after major vendor changes or when your sending architecture shifts.

Are forwarded messages failing SPF?

SPF evaluates the envelope sender domain, so classic forwarding often fails because the forwarder’s server is not in your SPF. This is a known limitation of SPF.

How to fix it, step by step:

• Focus on solutions that preserve or compensate for authentication during forwarding.
• Where possible, use forwarders that implement the Sender Rewriting Scheme (SRS) to keep SPF evaluable after hops.
• Sign outbound mail with DKIM so authentication survives forwarding and can pass DMARC alignment even if SPF fails.
• If you control the forwarder, enable SRS and document it for your help desk.

A simple policy note helps teams understand that SPF failures on forwarded mail are expected and that DKIM and DMARC should be the primary signals in those paths.

Is your SPF evaluating the wrong domain?

Receivers check the domain in the SMTP “Mail From” (return-path) or the HELO domain, not the human-visible From header. If your ESP uses a custom return-path, your SPF must authorize that return-path domain, not only your visible brand domain. Misalignment here leads to confusing false negatives.

How to fix it, step by step:

• Confirm which envelope domain your providers use and align SPF accordingly.
• Send a test and capture the SMTP transcript or full headers to find the return-path domain.
• Publish or update SPF on the return-path domain, or ask the ESP to let you host a custom return-path under your domain.
• For DMARC alignment, either align Mail From to your organizational domain or rely on DKIM alignment from the same domain.

Are you using risky or deprecated mechanisms?

The ptr mechanism is discouraged because it is slow and unreliable. Overuse of exists can create heavy lookup chains. Loose include patterns can import more space than you need.

How to fix it, step by step:

• Prefer explicit, auditable entries.
• Remove ptr. Replace with specific ip4 or ip6 ranges or vetted include targets.
• Use exists only for advanced, provider-driven patterns and to measure the lookup impact.
• Keep evaluation order efficient by listing the most selective mechanisms first.

Is your SPF too large or hard to maintain?

TXT strings are limited to 255 characters per segment, though you can concatenate multiple strings. Very large records increase the risk of errors and are hard to operate.

How to fix it, step by step:

• Treat SPF like source-controlled infrastructure.
• Keep one authoritative record per domain and store the canonical version in version control.
• Use comments in your DNS management system to document vendor ownership and change dates.
• When length grows, split long TXT content into multiple quoted strings on publish, but keep the logical record simple.
• Review quarterly to remove retired services and rotate test traffic to catch regressions.

How can you set up SPF records correctly for your domain?

Setting up SPF is less about a one‑time TXT entry and more about establishing a repeatable, auditable process to protect deliverability:

• Inventory all senders – Include internal servers, marketing ESPs, and SaaS apps that send mail on your behalf.
• Draft the SPF record – Combine authorized IPs and include mechanisms into a single v=spf1 record.
• Publish to DNS – Add the TXT record in your registrar or DNS management platform.
• Validate and monitor – Use SPF testing tools and seed inboxes to catch misconfigurations before going to -all.
• Review quarterly – Maintain your record to reflect new services and retire old ones, preventing future mail failures.

This operational approach ensures that marketing, IT, and security teams stay aligned and your domain remains both protected and fully deliverable.

Always follow the same syntax structure when adding new domains. The easiest way to do this is to duplicate a successful SPF record TXT file and swap out the domain for the new, updated one.

For instance, sending emails from Google Workspace would look like:

Adding multiple domains at the same time to one record is also possible. Both Google and Mailchimp together would look like:

Additional qualifiers can be added to SPF records to make them more complex. A + or - will either authorize or fail the SPF record when an email is sent, while ~ denotes a softfail, where the message will be accepted but sent to spam instead of the recipient’s primary inbox. 

The softfailSoft can help messages be delivered if there is a slight mismatch in records, which can happen in larger organizations that maintain large numbers of SPF records when IP addresses are updated.

When should you combine SPF with DKIM and DMARC for full protection?

While SPF is a critical first layer of email authentication, relying on it alone leaves gaps that attackers and misconfigurations can exploit. SPF only verifies that the sending server is authorized to send for a domain — it doesn’t ensure the message hasn’t been altered in transit or that the visible “From” address aligns with your domain for recipient trust.

Why SPF alone isn’t enough

• Forwarded messages often fail SPF: When emails are forwarded, the forwarding server’s IP isn’t in your SPF record, causing authentication failures.
• No protection for message content: SPF doesn’t validate that the email body or attachments remain unchanged during delivery.
• Limited phishing protection: Attackers can still spoof your display “From”  address if they avoid the return-path checks that SPF uses.

How DKIM and DMARC close the gaps

DKIM (DomainKeys Identified Mail):

• Adds a cryptographic signature to each email that proves the content hasn’t been tampered with.
• Survives forwarding, which complements SPF’s weaknesses.
• Helps establish domain trust for mailbox providers evaluating sender reputation.

DMARC (Domain-based Message Authentication, Reporting & Conformance):

• Enforces alignment between the visible “From” domain and SPF/DKIM results.
• Allows you to instruct receivers to quarantine or reject mail that fails authentication.
• Provides detailed reports so you can monitor who is sending on behalf of your domain and catch abuse attempts.

Example path to full protection:

• Step 1: Implement SPF for all sending sources.
• Step 2: Sign all outgoing mail with DKIM.
• Step 3: Deploy DMARC in monitoring mode (p=none) to collect data on unauthorized activity.
• Step 4: Move to a stricter DMARC policy (p=quarantine or p=reject) once you are confident all legitimate senders pass SPF and DKIM.

By moving from SPF alone to a full authentication stack, businesses gain both technical protection and strategic visibility, making it easier to maintain trust and protect ROI in all outbound email programs.

Those emails aren't so phishy anymore...

Securing your domain with SPF is the first step toward reliable, trustworthy email communication. But true protection and the highest ROI from your email program comes from layering SPF with DKIM and DMARC.

Organizations that move to full authentication not only block spoofing attempts but also gain critical visibility through DMARC reporting, helping IT and marketing teams identify unauthorized senders and maintain strong inbox placement.

For any business handling sensitive communications or customer outreach, implementing SPF now and planning for full DMARC enforcement is no longer optional — it’s a fundamental part of safeguarding brand reputation and revenue.

Take your email security one step further with DomainKeys Identified Mail (DKIM), a private cryptographic key that acts as a secure email signature.