SPF and DMARC: The Key DNS Records for Reliable Email Deliverability

In today’s email landscape, even legitimate business emails can end up lost in spam folders or rejected outright if your domain isn’t properly authenticated. This is where DNS records like SPF (Sender Policy Framework) and DMARC (Domain-based Message Authentication, Reporting & Conformance) become critical. These email authentication protocols verify that you are who you claim to be as a sender, making it harder for spammers and fraudsters to impersonate your domain. Major email providers now effectively require such authentication – as of 2024, companies like Google, Yahoo, and Microsoft mandate protocols like DMARC for senders. Properly implementing SPF and DMARC (along with DKIM, DomainKeys Identified Mail) provides a framework to authenticate your emails, improve deliverability, and protect your domain from misuse. In this article, we’ll explain what SPF and DMARC are, why they matter, how they help when using your own servers and third-party platforms (Mailchimp, CRM tools, invoicing software, etc.), common pitfalls to avoid, and actionable steps to ensure your emails reliably reach their recipients.

What is SPF (Sender Policy Framework)?

SPF is essentially a DNS TXT record that lists all mail servers authorized to send email on behalf of your domain. Think of it as a “allowed senders” list for your domain. Whenever an email is received claiming to be from your domain, the receiving mail server checks the domain’s SPF record to see if the sender’s IP address is on that list. If the IP is authorized, SPF passes; if not, SPF fails, and the message may be flagged or rejected. This simple mechanism helps receiving mail systems verify the legitimacy of the sender.

An example SPF record might look like:

v=spf1 include:_spf.google.com ~all

In this example, v=spf1 signals the record is SPF, include:_spf.google.com means “also trust servers listed in Google’s SPF record” (typical for Google Workspace senders), and ~all is a soft fail for any sender not on the list (meaning unauthorized senders should be marked as suspicious). A stricter alternative is -all (hard fail, telling receivers to reject any non-listed senders).

SPF for Multiple Services: Many companies use several email sending services – for example, one might use an email marketing platform (like Constant Contact or Mailchimp) plus a separate automation tool (like Klaviyo), and perhaps their own mail server. It’s important to combine all authorized senders into one SPF record. You should not publish multiple SPF TXT records for the same domain (having more than one will cause errors). Instead, include all necessary servers/domains in a single record. For instance, if you use two providers, your SPF record needs to have include: statements for both. This ensures any server legitimately sending on your behalf is listed and will pass SPF checks. Failing to include all legitimate mail sources can lead to SPF “fail” results and subsequent email rejections.

SPF and Email Delivery: Implementing SPF correctly boosts your credibility with recipient mail servers. If SPF passes, it’s one indication that the email isn’t forged. If SPF fails and the message isn’t otherwise authenticated, many inbox providers will distrust it – potentially shunting it to spam or rejecting it. Misconfigured SPF (e.g. syntax errors, missing entries, or exceeding DNS lookup limits) can cause emails to fail these checks, negatively impacting deliverability and exposing your domain to spoofing abuse. In short, a proper SPF record is an essential first line of defense for reliable email delivery.

What is DMARC (and how does it relate to SPF & DKIM)?

DMARC is a DNS record that works in conjunction with SPF and DKIM to give receivers instructions on how to handle emails that fail authentication. While SPF and DKIM are authentication methods, DMARC is a policy framework that says “if an email from my domain fails the SPF/DKIM checks, here’s what to do with it.” With DMARC, domain owners can tell recipients to reject or quarantine emails that don’t pass checks, or just monitor (no action) and report on them. The goal is to curb spam and phishing by making it much harder for unauthorized senders to spoof your domain.

How DMARC Works: When an email comes in, the receiver first evaluates SPF and DKIM:

If at least one passes and is “aligned” (meaning the domain in the SPF/DKIM matches the sender’s domain), then the email is considered authenticated under DMARC.
If both SPF and DKIM fail (or pass but not aligned with the from-domain), DMARC policy kicks in. The DMARC record (published as _dmarc.yourdomain.com in DNS) will specify a policy: typically p=none (monitor only), p=quarantine (treat failing mail as suspicious, e.g. send to spam), or p=reject (outright refuse failing mail).

For DMARC to consider an email fully authenticated, the domain alignment is key. This means the domain in the email’s “From” header should match the domain that passed SPF check (the bounce/return-path domain) or the domain used to sign the DKIM signature. Misalignment is a common issue – for example, if the return-path domain is a third-party service’s domain and not yours, an email could pass SPF but still fail DMARC alignment. We’ll discuss how to tackle that in a later section on pitfalls.

DKIM (DomainKeys Identified Mail): While our focus is SPF and DMARC, it’s important to mention DKIM because DMARC also relies on it. DKIM uses a pair of cryptographic keys: your outgoing mail server signs each email’s headers with a private key, and receivers verify it using your public key published in DNS. If the signature is valid, it proves the email hasn’t been tampered with and is genuinely from a server allowed by your domain. With DMARC, you’ll want your DKIM signatures to “align” with your domain (i.e., the DKIM signing domain (d=) should be your domain or a subdomain of it). That way, even if an email fails SPF (say, due to forwarding or other issues), a valid DKIM signature can still let it pass DMARC.

Why DMARC Matters for Deliverability: DMARC provides receiving servers confidence that “emails from @yourdomain.com are properly authenticated or should be discarded.” This greatly helps protect your brand from spoofing and phishing. From a deliverability standpoint, correctly authenticated emails (with SPF/DKIM passes aligned with DMARC) are far less likely to be flagged as spam or rejected by mailbox providers. Conversely, if you have a strict DMARC policy and your messages aren’t configured to pass it, you might unintentionally block your own legitimate emails – so setup and testing are crucial. We’ll outline how to safely deploy DMARC shortly.

Why SPF and DMARC Are Crucial for Reliable Email Delivery

Trust and Inbox Placement: Email providers (like Gmail, Outlook, Yahoo, etc.) use SPF and DMARC checks as signals for whether an incoming message is trustworthy. When your DNS is set up with SPF and DMARC (and DKIM) and everything passes, it tells the provider that the email truly comes from your domain and hasn’t been spoofed. As a result, the message is far more likely to land in the inbox. If you don’t have these records – or they’re configured incorrectly – providers may treat your messages with suspicion. In fact, whether a message is delivered or dropped/marked spam often hinges on authentication results. According to industry data, organizations that implement SPF, DKIM, and DMARC see significantly fewer malicious or fraudulent emails reaching users, and correctly authenticated emails avoid the spam folder in the vast majority of cases.

Protection Against Spoofing: Beyond deliverability, SPF and DMARC protect your domain’s reputation. SPF ensures only authorized servers can send as your domain, and DMARC with a quarantine/reject policy can outright block spoof emails purporting to be from you. Without these, attackers could send phishing emails pretending to be your company (since nothing in DNS says they can’t), and recipients’ servers would have no automatic way to tell those are fake. Poor authentication setup can thus lead to your domain being used in spam or phishing – damaging your brand and possibly getting your domain blacklisted. By contrast, a solid SPF/DKIM/DMARC setup helps bolster your sender reputation and keep your legitimate emails flowing smoothly to clients, while keeping bad actors at bay.

Compliance and Requirement by Providers: As mentioned earlier, the email ecosystem is moving toward universal adoption of these standards. Many cloud email services and third-party senders now require you to configure SPF/DKIM/DMARC when using your domain. Some, like Google Workspace and Microsoft 365, strongly recommend it for all customers to prevent deliverability issues. In fact, Google and Yahoo have made having a proper DMARC policy a de-facto requirement for large-scale senders. The takeaway for businesses is clear: if you want reliable email delivery, implementing SPF and DMARC is no longer optional – it’s essential.

SPF & DMARC in Practice: Own Mail Servers vs. Third-Party Services

Not all business emails originate from the same place. You might send some via your company’s own mail server (or web server), and others via third-party platforms (marketing tools, CRM systems, invoicing software, etc.). SPF and DMARC are just as important in the latter cases, but there are a few nuances:

Sending from Your Own Server or Domain Email

If your organization runs its own mail server (or you use your web server to send emails from applications), you must ensure that server is listed in your SPF record. This typically means adding the server’s IP address or hostname to the SPF TXT entry (e.g., using an ip4: mechanism or an include: if your mail is routed through a provider). Also, configure reverse DNS (PTR) for your mail server’s IP if possible – many receivers check that the IP has a PTR record matching your domain, and lacking this can hurt deliverability. (Reverse DNS isn’t part of SPF/DKIM/DMARC, but it’s a complementary DNS check that further validates your server.)

For your own mail server, implementing DKIM is highly recommended: generate a DKIM key pair and publish the public key in DNS, so outgoing mail gets signed. This and a proper SPF entry for your domain’s MX or sending IP will maximize the chances that receivers trust your mail. Finally, publish a DMARC record for your domain to enforce these checks. Start with a monitoring policy (p=none; rua=mailto:you@yourdomain.com) to collect reports on your mail streams, then ratchet up to quarantine or reject once you’re confident legit mail is passing authentication.

Using Third-Party Email Platforms (Mailchimp, CRMs, Invoicing Software, etc.)

It’s very common to use external services to send emails on your behalf. For example, you might use Mailchimp to send a newsletter, Salesforce or HubSpot to send CRM emails, or an invoicing app to email customer receipts. In these cases, additional SPF and DKIM configuration is usually needed so that these services are authorized to send as your domain.

Most reputable third-party email platforms will provide instructions to “authenticate” your domain. Typically, this involves:

Adding an SPF include: e.g., if newsletterservice.com sends your emails, they may ask you to add include:newsletterservice.com (or their specific SPF subdomain) to your SPF record. This ensures their mail servers are considered valid senders for your domain. Failing to include a service’s mail servers in SPF can result in SPF failures for all those emails (since from the receiver’s perspective, the emails are coming from servers not on your list). For instance, if your accounting software sends via SendGrid or Amazon SES, you’d need to include those in SPF or use a provided include mechanism.
Enabling DKIM signing: Many platforms let you configure DKIM by providing you with a DNS record (often a CNAME or TXT) to publish. This allows them to sign emails with a DKIM key tied to your domain, which will pass DKIM checks. DKIM is especially important if SPF alignment can’t be achieved (more on alignment below). For example, Mailchimp no longer requires adding an SPF include for their servers – their emails may fail SPF alignment by design – but they rely on DKIM signatures to authenticate your domain instead. In such cases, setting up DKIM is crucial so that those emails still pass DMARC via DKIM (even if SPF fails).
Domain verification: Many services require verifying you own the domain (often via a link in an email or adding a TXT record) before they’ll send using your domain in the “From” address. This is a preliminary step to prevent abuse.

Pitfall – SPF Alignment and Return-Path: One tricky aspect with third-party senders is SPF alignment under DMARC. SPF checks use the envelope sender (a.k.a. return-path or bounce address) domain. Often, services send your emails using their own bounce address (e.g., bounce@service.com), not your domain. This means that even if you include their servers in SPF and SPF passes, the domain that passed SPF is service.com, which does not match your domain in the “From” header – hence DMARC’s SPF alignment fails. This is why some services forgo SPF in favor of DKIM for DMARC purposes. It’s also why certain providers let you set up a custom return-path domain (like a subdomain of your domain) so that SPF can align. If given that option, it’s good to use it – for example, configuring a custom bounce domain like bounces.yourdomain.com that the service will use, so that SPF checks align with your parent domain.

In summary, when using third-party platforms: always follow their DNS setup instructions. Ensure you’ve added any required SPF include for their sending domains (unless they explicitly say not to), publish their DKIM key records on your domain, and double-check that these messages are passing DMARC alignment. It’s easy to overlook this when adding a new service – a common mistake is starting to send emails through a new tool but forgetting to update SPF/DKIM, resulting in sudden deliverability problems.

Common SPF and DMARC Pitfalls (and How to Avoid Them)

Even with the right concepts in mind, there are some frequent misconfigurations that plague SPF, DKIM, and DMARC setups. Here are the most common pitfalls and how to address each:

Multiple SPF Records: DNS permits only one SPF record per domain. If you accidentally create a new TXT record for SPF while an old one exists (instead of merging them), both records become invalid. This can lead to SPF permanent errors or failed checks. Fix: Always maintain a single SPF entry. When you need to add a sender, edit the existing SPF string to include it, rather than adding a second record.
Exceeding DNS Lookup Limits: An SPF record can contain at most 10 DNS lookups (caused by includes, redirects, etc.). If you use many email services, all those includes can add up and break the 10-lookup rule, causing SPF to fail (receivers will see a “permerror”). Fix: Keep includes to only those truly needed. You can often omit redundant entries and/or use SPF “flattening” tools to convert includes into a list of IP addresses to cut down lookups. Regularly audit your SPF record for services you no longer use, and remove unnecessary includes.
Incomplete SPF Authorization: Forgetting to list a legitimate sending source in SPF is another common issue. The result is straightforward – emails from that source will fail SPF and likely be rejected or marked spam. Fix: Inventory all services that send email for your domain (including that no-reply address from your website, your CRM system, HR tools, etc.) and make sure every one of them is accounted for in your SPF. Update the record whenever you add or change providers.
SPF Syntax Errors: Something as small as a typo can break your SPF record. Missing spaces, incorrect mechanisms, or not wrapping the entire policy in quotes (depending on your DNS interface) can invalidate the record. Fix: Use an SPF record generator or checker tool to validate the syntax. And remember the correct format: start with v=spf1, list mechanisms (include/ip4/ip6/a/mx, etc.), and end with an ~all or -all.
DKIM Not Set or Misaligned: Some businesses skip DKIM setup, which leaves an authentication method on the table. Others enable DKIM but encounter DKIM alignment issues. Alignment means the domain in the DKIM signature (the d= value) should match your sending domain. If, for example, your email’s From is user@yourdomain.com but the DKIM signature is signed by thirdparty.com, then even if the signature is valid, it won’t count for DMARC alignment. Fix: Always publish the DKIM public key provided by your email platform in your domain’s DNS and ensure the service is signing emails as your domain. Many services let you specify the signing domain (often your own domain once verified). Test DKIM using tools or by sending to a mailbox at Gmail/Outlook and checking the email headers for DKIM-Signature to see the domain. Ensure the d= domain matches exactly (or is a subdomain under your domain if you use relaxed alignment).
Missing or Misconfigured DMARC: Not having a DMARC record means you’re missing out on the benefits of instructing receivers and getting feedback. But having a DMARC record with a bad setup is risky too. Common mistakes include setting a strict policy (p=reject) too soon without monitoring, or conversely leaving p=none forever (which doesn’t actively protect you). Another mistake is not using ruf/rua to receive reports, or ignoring the reports that are sent. Fix: Start with p=none and a valid email in rua to collect aggregate reports. Review the reports to identify any sources failing authentication (they can reveal misconfigurations or unauthorized use). Once you’re confident all legitimate mail sources are aligned and passing, move to p=quarantine or p=reject to enforce protection. Also consider subdomain policies (sp= tag) if you want to control or lock down subdomains separately. Remember to monitor on an ongoing basis – if you add a new sender and it shows up as failing in DMARC reports, take action before it impacts email delivery.
Domain Alignment Across Services: As discussed, a frequent pitfall is not addressing domain alignment when using third-party services. For example, using Mailchimp or AWS SES “out of the box” without setting up your domain will result in those emails failing DMARC (since they’ll appear to come from yourdomain.com but aren’t properly aligned). Similarly, having a mismatch between the Return-Path (bounce address) domain and your From domain can break SPF alignment. Fix: Whenever you use a new service, always configure the provided authentication settings (SPF include, DKIM, verified custom domain or return-path). If a service doesn’t support domain alignment, you may choose to send those particular emails from a distinct subdomain of your domain (with its own SPF/DKIM/DMARC) to isolate and manage alignment issues.

By being aware of these pitfalls, you can double-check your DNS records and sending practices to avoid the common errors that lead to deliverability headaches.

Consequences of Poor SPF/DMARC Configuration

It’s worth underscoring what can go wrong if SPF and DMARC are not properly set up, as the consequences can be serious for a business:

Emails Landing in Spam or Not Being Delivered: This is the most immediate impact. ISPs will often flag or refuse messages that fail SPF/DKIM/DMARC checks. If you’ve ever had customers say “I didn’t get your email” or noticed open rates plummet, an authentication failure could be the culprit. Without correct SPF/DKIM, your emails might get marked as spam or rejected outright, disrupting communication and marketing efforts.
Damage to Sender Reputation: Repeatedly failing authentication can harm your sending reputation. Mail providers use your domain’s history to decide if you’re a spammer; if many emails from you fail SPF or DMARC, it looks like you don’t control your sending or (worse) that spammers are spoofing you. This can make even future properly authenticated emails more suspect. Also, a misconfigured DMARC (like an unmonitored p=reject that is blocking legitimate mail) can inadvertently cause your domain to appear untrustworthy (due to bounces) unless quickly fixed.
Spoofing and Phishing Risks: If you don’t publish an SPF record or DMARC policy, it’s open season for attackers to forge emails from your domain. Your customers or partners could receive fake emails that appear to come from you (e.g., phishing emails attempting fraud). Such incidents can lead to financial loss and erode trust in your brand. A misconfigured SPF (like too lenient +all mechanism or expired include) similarly leaves gaps for spoofing. On the flip side, a strong SPF and DMARC setup significantly reduces successful impersonation attempts, with businesses reporting dramatically fewer phishing emails reaching their employees once these measures are in place.
Delivery Failures for Transactional Emails: Some of the most critical emails (password resets, invoices, system alerts) are often sent by automated systems or third-party tools. If those emails fail authentication, they might never reach the user, leading to poor user experience or even operational problems. For instance, an invoice that never arrives can delay payment, or a missed alert could disrupt service. Ensuring those systems are authenticated (via SPF/DKIM and passing DMARC) is crucial for reliability.
Troubleshooting Nightmares: Without DMARC reports, you may not even realize there’s a problem until a lot of emails have been lost. Then your team scrambles to figure out why emails are failing. Proactively having DMARC with reporting (and monitoring those reports) can save you from this reactive firefighting by highlighting issues early.

In short, poor SPF/DMARC configuration can lead to communication breakdowns, security incidents, and a damaged reputation. The good news is that these are preventable issues – with the right setup, you can maintain a strong sender reputation and high deliverability.

Actionable Recommendations for Reliable Email Deliverability

To ensure your emails reach the inbox and your domain stays protected, here are actionable steps and best practices:

Audit Your Email Senders: Make a list of all services and servers that send email using your domain. This includes your main mail server, web apps, marketing platforms, CRM systems, customer support tools, billing/invoicing software – everything. This inventory will drive your SPF includes and DKIM setup. It also helps you spot any sender that shouldn’t be there.
Create a Single, Comprehensive SPF Record: Consolidate all the sources from step 1 into one SPF TXT record for your domain. Use include: mechanisms for third-party services (as specified by their documentation) and/or IP addresses for your own mail servers. Ensure you don’t exceed 10 DNS lookups – if you’re near the limit, consider removing redundant includes or using a flattening tool to compress the record. Publish the SPF record and then test it (using online SPF checkers) to verify it’s valid. Remember to update this record whenever you add or remove a sender (stale DNS records can cause issues down the line).
Enable DKIM for All Email Sources: For each platform or server that can send as your domain, set up DKIM signing. This usually means generating a public/private key pair (or having the service provide one) and adding a DNS TXT record (often under selector._domainkey.yourdomain.com). Once in place, verify that emails from that source include a DKIM-Signature header and that it passes validation. DKIM adds a layer of protection and is particularly useful if emails get forwarded (which can break SPF) – as long as the DKIM stays intact, the email can still be authenticated downstream.
Publish a DMARC Record (Start with Monitoring): Add a _dmarc.yourdomain.com TXT record with at least v=DMARC1; p=none; rua=mailto:your-report@yourdomain.com. The p=none policy means no emails will be blocked; instead, you’ll receive aggregate reports about SPF/DKIM passes and fails. Use this phase to spot misconfigurations or unknown senders. It’s recommended to use a DMARC report analyzer tool or service to aggregate and visualize these reports for easier analysis. Over a few weeks, you should be able to identify if any legitimate emails are failing SPF/DKIM. Fix those issues as needed (e.g., update SPF includes, configure DKIM for that sender, etc.).
Move to Enforcement Gradually: Once your monitoring shows all legitimate mail is authenticating properly, change your DMARC policy to p=quarantine (perhaps with pct=50 to start, affecting 50% of mails) or straight to p=quarantine at 100%. This will direct failing mails to spam/junk. Monitor for any unexpected side effects. Finally, move to p=reject when confident – this instructs ISPs to drop emails that fail authentication entirely. By doing this gradually, you avoid accidentally blocking important emails while moving toward full protection. Always leave your report addresses (rua and optionally ruf) in place so you continue to get feedback even after enforcement.
Align Your Domains (If Using Third Parties): As part of the above, ensure that for each third-party service, you’ve achieved domain alignment. This may involve setting the service’s “From address” to use your domain (after domain verification) rather than a generic address. It might also involve configuring a custom return-path domain or subdomain they provide. Check DMARC reports or use tools to simulate an email from each service to verify that either SPF or DKIM (or both) pass with alignment. If a service cannot send with your domain in a DMARC-aligned way, consider using a subdomain for that service’s emails and adjust the DMARC policy for that subdomain separately (sp= tag can specify subdomain policy).
Use Testing Tools: Take advantage of free tools to test your email authentication. For example, services like Mail-tester, MX Toolbox, or specific SPF/DKIM/DMARC checkers will analyze an email you send them or inspect your DNS records. These can catch issues like DNS propagation problems, syntax errors, or missing includes. Some tools will also flag if your SPF is too long or if you’re nearing the lookup limit.
Monitor and Maintain: Setting and forgetting is dangerous in the email world. Designate someone or use a service to monitor DMARC reports continuously. This will alert you if, say, a new source starts sending unauthenticated email claiming to be your domain (could be a sign of compromise or a new third-party you forgot to configure). Also review your SPF/DKIM whenever you change email providers or add a new sending service – outdated records (like pointing to a deprecated service) can cause hard-to-track issues months later. Regularly rotating DKIM keys (where possible) is another security best practice.
Educate Your Team and Clients: Make sure your developers and IT staff understand at least the basics of SPF, DKIM, and DMARC. This helps ensure that when new projects or tools are adopted, email authentication is part of the setup checklist, not an afterthought. For clients (if you’re a development agency setting up things for them), explain why these DNS records are needed in non-technical terms – e.g. “This will prevent your invoice emails from going to spam and will protect your brand from email spoofers.” In our experience at Origami.Vision, taking a proactive stance on email authentication saves everyone headaches down the road.
Consider Subdomain Delegation for Third-Parties: If you use a lot of different third-party senders, managing everything under one root domain can get complex. One strategy is to give each major function a subdomain. For example, use news.yourdomain.com for newsletters via Mailchimp, billing.yourdomain.com for invoices via your billing software, etc. You can then publish SPF/DKIM/DMARC records on those subdomains specifically, without cluttering the primary domain’s SPF or risking one service’s issues affecting another. Receivers still see the emails as coming from your organization (just a subdomain variation), and you gain flexibility. Keep in mind, though, that DMARC’s default is to inherit top-level policy for subdomains unless you specify sp=, so if you use this approach, configure the sp tag or explicit records on the subdomain.

By following the above steps, you’ll create a robust email authentication stance. This means better deliverability – your messages reliably reach inboxes – and better security, as you prevent others from abusing your domain. Well-implemented SPF, DKIM, and DMARC work in tandem to ensure that you and only you control who can send emails as your domain, and that those emails earn the trust of mailbox providers.

Conclusion

Email deliverability can make or break your communication with clients and users. As a development agency familiar with the pitfalls of transactional and marketing emails, we know that a little upfront work in DNS records saves a lot of trouble later. SPF and DMARC are indispensable tools in this regard – they verify your emails’ legitimacy and keep your domain’s reputation intact. Implementing them (along with DKIM) might require a bit of technical effort, but the payoff is clear: fewer emails in spam, fewer lost messages, and a stronger defense against spoofing. In summary, investing time in SPF and DMARC configuration is investing in your business’s reliability and credibility in every inbox. With the actionable tips provided, both developers and business owners can ensure their email infrastructure is solid. Here’s to safer and more successful emailing, backed by the right DNS records and policies!