It’s mind-blowing sometimes to think about everything that goes on behind the scenes when you click on “Send” after writing an email. In seconds, your message goes on a complex journey—getting relayed over networks, through authentication checkpoints, and under multiple security layers before it arrives in your recipient’s inbox (or, if luck’s not in your favor, their spam folder).
SPF (Sender Policy Framework) is an important authentication protocol used to make sure that your email arrives safely. Designed to prevent spoofing and phishing, SPF enables mail servers to check whether an email originated from an authorized source. But SPF alone is not immutable and it must be properly aligned with the sender’s domain in order to truly work.
SPF record configuration issues, alignment mismatch issues, third-party sending services, and other issues can cause rejection, spam filtering, and deliverability nightmares. This is why SPF alignment issues should matter to IT administrators, email security experts, and marketers who use email in their business growth and communication.
What is SPF alignment?
SPF alignment means that the domain used in the Return-Path (also called the “envelope-from” or “MailFrom” domain) matches the domain in the From address that the recipient sees in their inbox.
- If these domains are the same or share the same root domain (depending on the alignment mode), SPF alignment passes.
- If they are different, SPF alignment fails, which can affect DMARC authentication and potentially result in emails being rejected or marked as spam.
How SPF alignment works
When an email is sent, the recipient’s mail server checks the SPF record of the sending domain to verify if the sending server is authorized. However, for SPF to be fully effective under DMARC policies, it must be aligned with the domain in the email’s visible From address.
SPF alignment can be applied in two ways:
- Strict Alignment → The Return-Path domain must be an exact match to the From address domain.
- Relaxed Alignment → The domains must share the same root domain (e.g., mail.example.com aligns with example.com).
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Scenario
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Return-Path (Envelope-From)
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From Header
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SPF Alignment Result
|
|---|---|---|---|
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Strict Alignment Pass
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mail.example.com
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mail.example.com
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Pass
|
|
Relaxed Alignment Pass
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mail.example.com
|
example.com
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Pass
|
|
Alignment Fail
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bounce.thirdparty.com
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example.com
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Fail
|
SPF alignment example
Pass:
- Return-Path: bounce@example.com
- From: user@example.com
(These match under both strict and relaxed alignment.)
Fail:
- Return-Path: bounce@mail.example.com
- From: user@example.com
(Relaxed alignment passes, but strict alignment fails.)
If SPF alignment fails, emails may not comply with DMARC policies, leading to increased rejection or placement in spam.
Why is SPF alignment important?
It prevents email spoofing & phishing
SPF alignment allows only authorized servers to send emails using your domain. If an attacker attempts to send spoofed emails from a different mail server, SPF alignment will fail, allowing phishing attempts to be identified more easily.
It ensures DMARC compliance
SPF alignment should pass for DMARC policies to pass too. If SPF is detected to be misaligned and DKIM is not used, DMARC can reject or quarantine emails and as a result, even legitimate messages may not get to recipients.
🔖 Related reading: SPF, DKIM, and DMARC: Boosting Email Security and Deliverability
It improves email deliverability
Emails that do not align with SPF may be considered spam or even rejected. Alignment improves inbox placement, creating a lower risk of the email going into the spam folder.
It avoids mail rejection due to third-party services
A lot of businesses will send out emails through third-party email providers such as SendGrid, Mailchimp, HubSpot, and Amazon SES. When security features like SPF are not properly set up, emails sent through these services will fail validation checks, causing emails to be improperly delivered.
It complies with modern email security standards
Large email providers such as Google, Microsoft, and Yahoo! are tightening email authentication standards. One of the main points that determines compliance and high sender reputation is SPF alignment.
Common SPF alignment issues & their causes
SPF alignment failures can lead to email rejections, spam filtering, and poor deliverability, often without senders realizing it. The main reasons for SPF alignment failures stem from misconfigured settings, forwarding issues, or improper domain alignment when using third-party services. Below, we break down the most common SPF alignment issues and their root causes.
1. Mismatched sending domains
One of the most frequent SPF alignment issues occurs when the Return-Path (MailFrom domain) does not match the From address domain. This happens when:
- Your domain (example.com) is used in the From address, but the Return-Path (envelope sender) is set to a different domain (e.g., mail.thirdparty.com).
- Many email marketing and transactional email services automatically use their own Return-Path, which breaks SPF alignment if not properly configured.
2. Email forwarding issues
Email forwarding is a major cause of SPF failures because it breaks the original SPF check. When an email is forwarded, the recipient’s mail server checks SPF against the forwarder’s IP address instead of the original sender’s. Since the forwarding server is not listed in the original SPF record, the email fails SPF validation.
Example of a forwarded email (Fails SPF check):
- Sender: [email protected] (SPF passes when sent directly).
- Forwarder: [email protected] (SPF check is now performed against the forwarder’s IP).
- Recipient: [email protected] (Receiving server checks SPF for the forwarder instead of the original sender).
Result: SPF fails because the forwarder’s IP is not authorized in the original SPF record.
3. Missing or misconfigured SPF records
An incorrect SPF record can cause alignment failures. Issues include:
- Using multiple v=spf1 records: SPF only allows one v=spf1 record per domain. Multiple records will cause validation errors.
- Exceeding the 10 DNS lookup limit: SPF has a hard limit of 10 DNS lookups. If exceeded, SPF fails automatically.
- Incorrect syntax or missing mechanisms
4. Third-party email services (Marketing & transactional emails)
If you’re using email marketing or transactional emailing with tools like Mailchimp, SendGrid, HubSpot, Salesforce, or AWS SES, SPF alignment can be invalid by default because these providers use their own Return-Path domain. During the process of sending emails on behalf of your domain, the provider often sets the Return-Path to its own domain. SPF alignment fails because the Return-Path (bounce.mailchimp.com) does not match your From address (example.com).
5. DMARC policy enforcing SPF alignment
DMARC needs either SPF or DKIM to pass—but if SPF alignment breaks and DKIM is not configured, emails may get quarantined or rejected. A strict DMARC policy (e.g., p=reject) without properly configured SPF and DKIM can cause harm by blocking legitimate emails.
How to fix SPF alignment issues
Unlike good SPF alignment, bad SPF alignment can be quite problematic for email authentication, deliverability, and security. SPF alignment failures can occur due to misconfigured SPF records, third-party sending services, and strict DMARC policies. Here, we walk through how to resolve those alignment issues so your emails end up in the inbox.
1. Configure SPF records correctly
SPF records must be properly structured and optimized to prevent authentication failures. Common issues include multiple SPF records, exceeding the 10 DNS lookup limit, or missing necessary include: mechanisms.
- Use a single SPF record (multiple v=spf1 records cause failure).
- Avoid exceeding 10 DNS lookups (include: mechanisms count towards this limit).
- Ensure all authorized mail servers are included (include:_spf.example.com).
Example of a proper SPF record:
v=spf1 include:_spf.google.com include:mailgun.org ~all
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SPF Mechanism
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Purpose
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|---|---|
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include:_spf.google.com
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Authorizes Google Workspace to send emails on behalf of the domain.
|
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include:mailgun.org
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Authorizes Mailgun (transactional email provider).
|
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include:mailgun.org
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Soft fail (unauthorized senders will still be delivered but flagged).
|
2. Align the Return-Path with the From domain
As mentioned above, a very common cause of SPF alignment failure is that the domain in the Return-Path (also called the MailFrom or Envelope-From) does not match the domain in the From address.
How to set a custom Return-Path:
To fix SPF alignment issues when using third-party email services:
- Go to the email provider’s authentication settings (e.g., Mailchimp, SendGrid).
- Look for the option to set a custom Return-Path (or Envelope Sender).
- Enter a Return-Path domain that matches your From address (e.g., bounce.example.com)
Example of correctly aligned domains:
- Return-Path: [email protected]
- From: [email protected]
3. Use DKIM to ensure DMARC passes
If SPF alignment is problematic (e.g., due to email forwarding), enabling DKIM (DomainKeys Identified Mail) can help ensure DMARC compliance. DKIM provides a digital signature that allows recipient servers to verify email authenticity, even if SPF alignment fails.
Unlike SPF, DKIM does not rely on IP addresses, so it remains intact even if an email is forwarded. DMARC only requires either SPF or DKIM to pass—so if SPF alignment fails, DKIM can still ensure compliance.
How to enable DKIM signing:
- Log in to your email provider’s control panel (Google Workspace, Microsoft 365, etc.).
- Generate DKIM keys (public and private).
- Add the DKIM public key to your domain’s DNS records as a TXT entry.
- Enable DKIM signing for all outgoing emails in your provider settings.
Example of a DKIM DNS record:
Name: default._domainkey.example.com
Type: TXT
Value: v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3…
4. Adjust DMARC policies cautiously
A strict DMARC policy can cause email rejections if SPF alignment is not properly configured. If emails are failing due to SPF misalignment, consider adjusting DMARC settings gradually:
- p=none: Monitors failures without rejecting emails.
- p=quarantine: Places failing emails in spam.
- p=reject: Blocks failing emails (use with caution).
Recommended DMARC record for SPF alignment issues
v=DMARC1; p=none; rua=mailto:[email protected];
- p=none allows monitoring without rejecting emails.
- rua=mailto:[email protected] enables reports for analysis.
Once SPF alignment is fully fixed, you can gradually move to p=quarantine and eventually p=reject to strengthen email security.
5. Use SPF check & testing Tools
Testing your SPF records regularly helps identify misconfigurations and alignment issues before they impact email deliverability.
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Tool
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Purpose
|
|---|---|
|
MXToolbox SPF Checker
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Checks SPF record validity and errors.
|
|
Google’s Check MX Tool
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Tests SPF, DKIM, and DMARC settings.
|
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DMARC Analyzer
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Monitors DMARC compliance and SPF alignment.
|
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SPF Flattening Tool
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Reduces SPF DNS lookups by optimizing records.
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Warmy also has free SPF and DMARC Record Generators for the configuration of SPF records and. Additionally, it helps with authentication, prevents phishing and legacy and instructs email recipients how to handle messages that fail authentication. Using these tools, you can regularly test and optimize your SPF configuration to prevent failures and improve email authentication.
Why SPF alone is not enough to guarantee email deliverability
While SPF (Sender Policy Framework) is a critical component of email authentication, it is not a complete solution for ensuring that emails reach the inbox. Many businesses mistakenly assume that having a properly configured SPF record is sufficient to prevent email spoofing, phishing, and spam filtering issues. Even if SPF, DKIM, and DMARC are all properly set up, email deliverability depends on more than just authentication. Email providers use complex filtering algorithms that consider multiple factors beyond SPF records.
Key factors that impact inbox placement
Engagement metrics (opens, replies, spam complaints)
Email providers like Gmail and Outlook prioritize emails with high engagement. Low open rates, high bounce rates, or excessive spam complaints hurt deliverability, even if authentication passes.
🔖 Related Reading: Why are My Emails Going to Spam or Junk? [Solved]
IP and domain reputation
Sending from a blacklisted IP or domain will cause emails to go to spam, even if SPF is valid. Warm up new domains to establish a positive sending reputation before sending large email volumes.
Proper warmup for new domains
Sending too many emails too quickly from a new domain triggers spam filters. Using a gradual warmup process (increasing volume over time) helps establish trust with email providers.
Content & formatting issues
Spammy subject lines, excessive links, or all-caps text can trigger spam filters. Avoid misleading or aggressive language to prevent spam classification.
Experience deliverability success beyond SPF with Warmy.io
Warmy.io goes beyond SPF to provide a complete deliverability solution, ensuring that your emails not only pass authentication but also land in the inbox and drive engagement. It is more than just an SPF checker—it’s a full-service email deliverability platform that optimizes every stage of your email-sending process.
Free SPF Record Generator & DMARC Record Generator
Setting up email authentication shouldn’t be complicated. That’s why Warmy.io offers free tools to help businesses generate and validate SPF and DMARC records with ease.
Warmy.io’s Free SPF Record Generator helps you:
- Generate a valid SPF record in seconds—just enter your domain and email provider.
- Automatically optimize your SPF record to avoid lookup limit failures.
- Validate your current SPF setup to identify errors and missing entries.
Meanwhile, Warmy.io’s Free DMARC Record Generator helps you:
- Create a valid DMARC record based on your email security needs.
- Monitor authentication failures to detect unauthorized senders.
- Gradually enforce DMARC policies to prevent email rejections.
AI-powered email warmup to build a strong sender reputation
A poor sender reputation can still cause emails to land in spam. There are many factors that contribute to your sender reputation and that’s why email warmup is essential—for ensuring that your emails build trust with mailbox providers before reaching full-scale sending.
For example, new email domains need to be gradually introduced to avoid spam filtering. A sudden spike in email volume can trigger blacklists and spam filters. Then, low engagement rates (low opens, high bounces) harm future deliverability. It’s a vicious cycle.
How Warmy.io’s email warmup works:
- Automatically yet gradually increases sending volume to build trust with mailbox providers.
- Simulates real human-like interactions—emails are opened, replied to, and marked as important, boosting deliverability.
- Works across 30+ languages so your emails look natural and relevant for global audiences.
Unlike traditional warm-up tools that rely on fake or bot-generated email interactions, Warmy.io uses advanced seed lists containing genuine email addresses—trusted mailboxes that engage with your emails like real recipients would. This further strengthens sender reputation across multiple email providers.
Free email deliverability test for diagnosing issues
Warmy.io’s Free Email Deliverability Test helps identify technical and reputation-based issues before they impact your campaigns. The test gives a comprehensive report of the percentage of your emails landing in the inbox, promotions, spam—and even the unreceived ones. It also reveals if your domain or IP is included in any blacklists—yet another major factor that affects deliverability. The test also checks your email authentication settings (SPF, DKIM, and DMARC) if they are properly authenticated.
All-new Domain Health Hub so you can always be a step ahead
If there’s one thing that keeps your emails consistently landing in inboxes, it’s domain health—and Warmy just made monitoring it easier and more powerful than ever. Instead of focusing on individual mailboxes, you can now monitor your deliverability at the domain level, giving you a broader, more strategic view of your email performance.
With the Domain Health Hub, you’ll be able to:
- Get a numeric health score based on key deliverability factors like inbox placement tests, DNS authentication, and Google Postmaster data—so you know exactly where your domain stands.
- Monitor spam rate trends, inbox placement, and overall deliverability performance with weekly or monthly tracking options—tailored to your needs.
- Ensure top-tier email authentication and security with comprehensive DNS Health Checks.
- Manage and track all your domains in one place, and easily zero in on which ones need urgent attention.
Experience seamless email deliverability with Warmy.io
Email deliverability is more than just keeping track of your SPF alignment. it’s about building a strong sender reputation, maintaining domain health, and ensuring that every email reaches the inbox. Warmy.io takes the complexity out of email optimization by providing a complete suite of deliverability tools, from real-time domain health monitoring, and AI-powered warmup.
Whether you’re a marketer, sales professional, or IT admin, Warmy.io gives you everything you need to prevent emails from landing in spam, boost engagement, and stay ahead of potential deliverability issues.
The best part? It’s all available to you today! Don’t let poor deliverability hold your emails back. Sign up for Warmy.io now (free for seven days!) and start sending with confidence.
