Why is SPF alignment inconsistent or not aligned and how does it affect email deliverability?
Michael Ko
Co-founder & CEO, Suped
Published 17 Apr 2025
Updated 18 Aug 2025
7 min read
Email authentication protocols are crucial for ensuring your messages reach the inbox, but sometimes what you see in one tool doesn't match another. It can be confusing when you check your Sender Policy Framework (SPF) setup and see inconsistent alignment, or even none at all. This often leaves senders wondering if their emails will make it to their recipients or end up in spam folders, impacting their overall email deliverability.
The perception of inconsistent SPF alignment, such as seeing 100% alignment on sending days and 0% on non-sending days in tools like Google Postmaster Tools, is a common source of confusion. This behavior can be perfectly normal depending on how email service providers (ESPs) handle sending domains. Understanding the nuances of SPF alignment and how it interacts with other protocols like DomainKeys Identified Mail (DKIM) and Domain-based Message Authentication, Reporting, & Conformance (DMARC) is key to solving this puzzle and improving your deliverability.
SPF (Sender Policy Framework) is an email authentication protocol that allows domain owners to specify which mail servers are authorized to send email on their behalf. It works by checking the `Return-Path` (also known as the envelope sender) domain of an incoming email against a published SPF record in the domain's DNS. If the sending server's IP address is listed, SPF passes.
SPF alignment, however, is a concept primarily tied to DMARC. For DMARC to pass using SPF, the domain in the `Return-Path` header must align with the `From` header domain (the one your recipients see in their email client). This alignment can be either relaxed or strict. When SPF passes but isn't aligned, it means the `Return-Path` domain is authorized, but it doesn't match your `From` domain.
It's important to differentiate between an SPF record simply passing and SPF aligning for DMARC. An SPF record can successfully authenticate the sending server's IP, yet the domain used for that authentication may not match your visible `From` domain. This is often the source of reported inconsistencies.
Understanding SPF and DMARC alignment
SPF checks the envelope sender (or Return-Path) domain. If the IP address of the sending server is authorized by the SPF record associated with this domain, then SPF passes. This is a crucial first step in email authentication.
DMARC requires either SPF or DKIM to be aligned with the From header domain for DMARC to pass. If SPF passes but the `Return-Path` domain doesn't match your `From` domain, SPF is considered unaligned for DMARC. However, if DKIM is present, passes, and aligns, your DMARC check will still succeed.
Why SPF alignment can be inconsistent
The primary reason SPF alignment can appear inconsistent, or not aligned at all, is the use of third-party email service providers (ESPs). When you send emails through an ESP, they often use their own domain in the `Return-Path` (or Mail From) header, not your From header domain. For example, if you send an email from marketing@yourdomain.com via an ESP, the `Return-Path` might be bounces@esp.com. In this scenario, SPF can still pass for esp.com, but it won't align with yourdomain.com.
The observation of 100% alignment on sending days and 0% on non-sending days is typical for DMARC reports. When you send emails, your ESP's `Return-Path` domain will pass SPF, and if your From domain also has a properly configured DKIM signature, DMARC will typically pass even if SPF is unaligned. On days when no emails are sent, there's no data to report, leading to 0% alignment. This is not an indicator of a problem, but rather how the reporting mechanism works.
Another factor is the type of SPF qualifier used. An -all qualifier (fail) will instruct recipients to reject emails that don't pass SPF, while a ~all qualifier (softfail) will allow them to be accepted but likely marked as spam. Forwards can also break SPF alignment, a common cause for issues if using -all.
Example SPF recordTXT
v=spf1 include:aspmx.sailthru.com -all
The impact of inconsistent SPF alignment on deliverability
While SPF alignment directly impacts DMARC results, it's not the only factor determining email deliverability. DMARC can pass if either SPF or DKIM align and pass. This means that even if SPF is unaligned, your email can still be authenticated and delivered if DKIM is properly configured and aligned. Many large senders operate with unaligned SPF (also known as a non-aligned envelope sender) because their ESP uses its own infrastructure for sending and bounce handling.
However, ignoring SPF alignment entirely might still have some subtle effects on your deliverability, especially with certain mailbox providers or filters that place a higher weighting on both SPF and DKIM aligning. While DMARC is the primary gatekeeper, a fully authenticated email (with both SPF and DKIM aligned and passed) presents a stronger signal of legitimacy. If your DMARC records are misconfigured, or if you lack a proper DKIM setup, unaligned SPF can quickly lead to emails going to spam or getting blocklisted.
Some sources suggest that while DMARC passes with one alignment, having both SPF and DKIM aligned can provide an incremental benefit to inbox placement. For a deeper dive into whether you should be concerned about unaligned SPF, read this perspective from Word to the Wise.
SPF pass, DKIM pass, DMARC pass (SPF unaligned)
Scenario: The `Return-Path` domain passes SPF, but it's different from the `From` header domain. The DKIM signature is valid and uses the `From` header domain, successfully passing and aligning for DMARC.
Deliverability impact: DMARC passes, so emails generally reach the inbox. Minor, if any, negative impact on deliverability. This is a common setup, especially with ESPs.
Scenario: The `Return-Path` domain passes SPF, but it doesn't align with the `From` header. DKIM either fails or is not present. Since neither SPF nor DKIM align and pass, DMARC fails.
Deliverability impact: Significant negative impact. Emails are highly likely to be rejected, quarantined, or sent to spam, leading to high bounce rates and potential IP or domain blocklisting.
Strategies for improving SPF alignment and deliverability
If you are experiencing deliverability issues that you suspect are related to SPF alignment, even if DMARC reports show a pass due to DKIM, there are steps you can take. The first and most impactful step is often to investigate why your email list is causing problems. Issues like poor list hygiene or low engagement can severely damage your sender reputation, overshadowing even perfect authentication. Addressing these foundational issues is critical for improving deliverability.
If your ESP allows for custom return-path domains (sometimes called white-labeling or private domains), you can configure your SPF to fully align with your From header domain. This involves adding a CNAME record that points to your ESP's domain for the `Return-Path` or `Mail From` domain. This ensures SPF will pass and align for DMARC. Always ensure your DKIM signature is also properly set up, as it provides a robust layer of authentication that can compensate for SPF non-alignment.
Finally, review your SPF record's qualifier. While -all (fail) provides the strongest protection against spoofing, it can also lead to legitimate emails being rejected, especially when forwarded. For many senders, a ~all (softfail) policy is a safer default. For more on the difference between relaxed and strict alignment, you can read this article.
Views from the trenches
Best practices
Actively clean email lists to remove inactive or problematic subscribers, reducing bounces and spam trap hits.
Prioritize email engagement metrics, as high engagement boosts your sender reputation with mailbox providers.
Implement DMARC with a policy of 'p=none' initially to gather reports and then gradually move to 'quarantine' or 'reject' as you gain confidence in your authentication.
Set up a dedicated sending subdomain for marketing or transactional emails to isolate their reputation from your main domain.
Common pitfalls
Misinterpreting SPF pass as SPF alignment, leading to DMARC failure if DKIM is not also aligned.
Failing to clean email lists, which directly contributes to higher bounce rates and poor sender reputation.
Using a strict '-all' SPF policy too early, which can cause legitimate forwarded emails to be rejected.
Ignoring DMARC reports, thus missing critical insights into authentication failures and potential spoofing attempts.
Expert tips
If using an ESP, configure a white-label domain for the `Return-Path` to ensure full SPF alignment.
Monitor deferral and rejection messages from mailbox providers to diagnose specific deliverability issues.
Use a '~all' (softfail) SPF policy instead of '-all' (fail) to avoid rejecting legitimate forwarded emails, which is a common scenario.
Always ensure your DKIM is robust and aligned, as it provides strong authentication even if SPF alignment is challenging.
Marketer view
Marketer from Email Geeks says they were told by their ESP to update their SPF record, but then their MXToolbox showed it was not aligned, while Google Postmaster Tools showed 100% alignment on sending days and 0% on non-sending days. This was confusing feedback to provide. They later discovered their soft bounce rate increased and they were blocked by Microsoft.
April 3, 2025 - Email Geeks
Expert view
Expert from Email Geeks says that SPF being valid but not aligned is normal and not a cause for panic. SPF is attached to the return path, which often belongs to the ESP and is different from the domain in the From header, which is what 'not aligned' means. DKIM being valid and aligned ensures DMARC still passes.
April 3, 2025 - Email Geeks
Navigating SPF alignment for better deliverability
SPF alignment can indeed appear inconsistent or unaligned due to the way email service providers manage the `Return-Path` domain. While an unaligned SPF doesn't automatically mean DMARC failure, especially if DKIM is properly configured and aligned, it's a factor that can contribute to deliverability challenges with some mailbox providers or if other authentication checks are weak.
The key to good email deliverability lies in a holistic approach that combines robust email authentication (SPF, DKIM, and DMARC) with strong sending practices, such as maintaining a clean and engaged email list. By understanding why SPF alignment behaves the way it does and implementing best practices, you can significantly improve your chances of reaching the inbox consistently.
