What steps to take when Gmail and Microsoft block emails after fixing an SPF failure?
Michael Ko
Co-founder & CEO, Suped
Published 11 Jun 2025
Updated 19 Aug 2025
6 min read
Dealing with email blocks from major providers like Gmail and Microsoft can be incredibly frustrating, especially after you've identified and fixed a foundational issue like an SPF failure. It's a common misconception that correcting the SPF record will instantly resolve all delivery problems. In reality, these blocks are often a symptom of broader trust and reputation issues that need a more comprehensive approach.
When your emails are getting bounced or sent to spam, even after an SPF fix, it indicates that recipient servers (ISPs) still perceive your sending domain or IP address as untrustworthy. This could be due to a prolonged period of sending with a misconfigured SPF record, which can severely damage your sender reputation. Recovering from such a situation requires strategic steps, patience, and diligent monitoring.
Before diving into solutions, it's crucial to distinguish between an IP-based block and a domain-based block. An SPF failure primarily impacts your domain's authentication, but persistent failures or other underlying issues can lead to your sending IP address being added to a blocklist (or blacklist) by ISPs. The bounce message you receive is your first clue.
Example bounce message indicating an IP blocktext
550 5.7.1 {hash}, messages from [a.b.c.d] weren't sent. Please contact your Internet service provider since part of their network is on our block list
If you see a message similar to the one above, the block is likely at the IP level, meaning your email service provider's (ESP's) network, or your own sending IP, is on a blocklist. In such cases, fixing your SPF might not immediately resolve the block because the IP address itself has a poor reputation. You can learn more about what happens when your IP gets blocklisted and how it affects deliverability.
IP versus domain blocks
Even with a corrected SPF, if the IP address you're sending from has a poor reputation or is on a blocklist, your emails will still be rejected. The focus then shifts from solely domain authentication to rehabilitating the sending IP's standing. This often requires working closely with your email service provider or understanding their shared IP policies.
Verify all authentication protocols
While you've fixed your SPF record, it's crucial to ensure your entire email authentication setup is robust. Modern email ecosystems rely on a trifecta of authentication protocols: SPF, DKIM, and DMARC. A strong SPF record is essential, but it works best in conjunction with the others.
DKIM: Ensure your emails are signed with a valid DKIM signature. This cryptographically links your email to your domain, preventing tampering.
DMARC: Implement a DMARC policy. This instructs receiving servers how to handle emails that fail SPF or DKIM. Even a p=none policy provides valuable reporting.
Major providers like Google and Microsoft have tightened their requirements, making proper authentication mandatory for deliverability. Google specifically states the need to set up SPF, while Microsoft emphasizes email authentication as a core component of their security measures.
Comprehensive authentication
A strong alignment of SPF, DKIM, and DMARC signals to recipient servers that your emails are legitimate and not spoofed. This is fundamental for rebuilding trust and improving your overall deliverability, especially with stringent providers like Gmail and Microsoft.
Contact postmaster teams and monitor reputation
Once you're confident that all your authentication records (SPF, DKIM, DMARC) are correctly configured and aligned, the next logical step is to reach out to the postmaster teams at Google and Microsoft. Both providers offer specific forms or channels for delisting requests or to report deliverability issues. This direct approach can expedite the process, especially if the block was primarily due to a long-standing SPF failure that has now been rectified.
Gmail postmaster
Use Google Postmaster Tools to monitor your sender reputation, spam rate, and authentication errors. If your IP or domain is blocked, you might find specific instructions or a request form within the tool or on their support pages. Being transparent about the SPF fix is helpful.
Even after contacting postmaster teams, continuous monitoring of your email deliverability metrics is essential. Pay close attention to bounce rates, spam complaint rates, and authentication pass rates. This ongoing vigilance allows you to catch and address new issues quickly, preventing further blocks.
You may also need to consider a rewarming strategy if your sender reputation has taken a significant hit. This involves gradually increasing your email volume over time to rebuild trust with ISPs. A sudden surge in email after a block can trigger new filtering mechanisms.
Address other potential red flags
While SPF was the identified culprit, other factors could contribute to ongoing blocking, especially if the SPF failure persisted for a month. ISPs consider many signals beyond just authentication.
Content quality: Review your email content for anything that might look like spam, such as excessive links, suspicious phrasing, or poor formatting.
Spam complaints: High spam complaint rates are a major red flag. Ensure your lists are clean and recipients have opted in.
Bounce rates: High bounce rates, especially for unknown users, signal a poorly maintained list. Regularly clean your email lists to remove invalid addresses.
Remember that improving email deliverability is a continuous effort. It's not just about fixing one issue but maintaining overall email health. Understanding why your emails go to spam involves looking at all these factors.
Leveraging DMARC reports for insights
DMARC reports provide invaluable insights into your email stream. Even if your DMARC policy is set to p=none, you'll receive XML reports from participating mailbox providers detailing how your emails are authenticating, which IPs are sending on your behalf, and which emails are failing authentication.
Metric
What to look for
SPF pass/fail rate
Ensure your SPF pass rate is consistently high after your fix. Any failures here need investigation.
DKIM pass/fail rate
Verify DKIM passes, as this provides a critical second layer of authentication, particularly important for providers like Google.
Alignment issues
Check if your organizational domain in the From header aligns with the domains in your SPF and DKIM records.
Source IPs
Identify any unexpected IP addresses sending email on your behalf. These could be unauthorized or indicate a misconfiguration.
DMARC monitoring allows you to see the real-world impact of your SPF fix and identify if other issues, like IP reputation, are still causing blocks. It's a critical tool for gaining visibility into your email deliverability.
Views from the trenches
Best practices
Ensure all email authentication protocols including SPF, DKIM, and DMARC are meticulously configured and consistently monitored.
Utilize Postmaster Tools from Google and Microsoft to gain insights into your sender reputation and identify block reasons.
Gradually increase your email sending volume after a block to rebuild trust with ISPs, a process known as rewarming.
Proactively engage with ISPs through their postmaster or delisting channels once all technical issues are resolved.
Maintain clean email lists by regularly removing invalid or unengaged addresses to reduce bounce rates and spam complaints.
Common pitfalls
Assuming that fixing a single issue, such as an SPF failure, will immediately resolve all email blocking problems.
Neglecting to investigate the full bounce message, which often provides specific error codes that indicate the true cause of the block, such as an IP block.
Overlooking the importance of DKIM and DMARC in addition to SPF, as modern email authentication relies on a layered approach.
Sending emails from an IP address that is on a blocklist without addressing the underlying reputation issues of that IP.
Failing to monitor ongoing deliverability metrics like spam complaint rates and bounce rates, which can lead to new blocks.
Expert tips
Carefully analyze bounce messages to determine if the block is IP-based or domain-based, as this dictates the next steps.
Understand that a strict SPF hard fail policy (`-all`) can lead to immediate rejections if authentication fails.
Consult with your email service provider if the block message points to their network or IP reputation.
Implement a DMARC policy, even a `p=none` policy, to receive valuable reports on authentication failures.
Regularly check major blocklists (or blacklists) to see if your sending IPs or domains have been listed.
Expert view
Expert from Email Geeks says: I recommend first using the official postmaster forms at Google and Microsoft once all technical issues are resolved.
June 28, 2024 - Email Geeks
Expert view
Expert from Email Geeks says: A failing SPF record alone might not be the primary cause of a hard block, especially if the email is also properly DKIM signed and authenticated.
June 28, 2024 - Email Geeks
Moving forward to sustained deliverability
Successfully recovering from an email block by Gmail and Microsoft after an SPF failure is a multi-faceted process. It goes beyond a simple fix and delves into a deeper understanding of email authentication, sender reputation, and ISP policies. By being proactive, comprehensive in your approach, and patient, you can restore your email sending capabilities.
Remember, email deliverability is a marathon, not a sprint. Continuous vigilance, adherence to best practices, and quick response to new issues are key to maintaining a healthy sending reputation and ensuring your emails consistently reach the inbox.
Dealing with email blocks from major providers like Gmail and 
Microsoft can be incredibly frustrating, especially after you've identified and fixed a foundational issue like an SPF failure. It's a common misconception that correcting the SPF record will instantly resolve all delivery problems. In reality, these blocks are often a symptom of broader trust and reputation issues that need a more comprehensive approach.
Google and Microsoft have tightened their requirements, making proper authentication mandatory for deliverability. Google specifically states the need to set up SPF, while Microsoft emphasizes email authentication as a core component of their security measures.
