How can I recover my domain's reputation after a spam attack blocked it on Gmail?
Matthew Whittaker
Co-founder & CTO, Suped
Published 4 May 2025
Updated 17 Aug 2025
7 min read
Discovering your domain has been blocked by Gmail after a spam attack can feel like a devastating blow. It means your legitimate emails, from marketing newsletters to critical transactional messages, are no longer reaching your audience. The immediate impact is often a sudden drop in email deliverability and significant disruption to communication flows.
This situation typically arises when your domain, or an IP address associated with it, has been used to send a large volume of unsolicited mail. Even if your systems were compromised, or a third-party service was exploited, the consequence is the same: your sender reputation takes a severe hit. Gmail, like other mailbox providers, uses sophisticated filters to protect its users, and a sudden surge in spam originating from your domain will trigger these defenses.
The good news is that reputation can be rebuilt, though it requires a strategic and sustained effort. It’s not an overnight fix, but by addressing the root cause, implementing best practices, and patiently demonstrating trustworthiness, you can restore your domain's standing with Gmail.
Immediate actions after a spam incident
The first critical step is to completely stop the source of the spam. If your domain was compromised, ensure all security vulnerabilities are patched. This might involve changing passwords, revoking API keys, or updating server configurations. Without halting the malicious activity, any efforts to recover your reputation will be futile, as the problem will persist.
Next, gather all available information about the block. Look at bounce messages you're receiving, as they often contain specific error codes or explanations from Gmail about why your emails are being rejected. These codes can point to issues like low sender reputation or blocklisting (or blacklisting) of your IP or domain. Also, verify your domain with Google Postmaster Tools, if you haven't already. This free tool provides crucial insights into your domain's reputation, spam rate, and authentication errors.
Example Gmail Bounce Message (unsolicited mail)
550 5.7.1 [IP_ADDRESS] Our system has detected that this message is likely unsolicited mail. To reduce the amount of spam sent to Gmail, this message has been blocked. Please visit https://support.google.com/mail/?p=UnsolicitedMessageError for more information.
Understanding these details is fundamental. Knowing whether it's an IP-based blocklist (or blacklist), a domain-level reputation issue, or a specific authentication failure helps you tailor your recovery strategy. Sometimes, a compromised CNAME record can lead to unexpected DMARC alignment and abuse, making it seem like your domain is sending spam when it's an old, forgotten DNS entry.
Strengthening email authentication
Email authentication protocols are the bedrock of good sender reputation. If your domain was exploited, chances are your SPF (Sender Policy Framework) record was either too permissive or misconfigured, allowing unauthorized servers to send emails on your behalf. Ensuring SPF, DKIM, and DMARC are correctly set up is paramount for recovery.
SPF defines which mail servers are authorized to send email from your domain. A proper SPF record with a hard fail policy (-all) instructs receiving servers to reject mail from unauthorized sources. DKIM (DomainKeys Identified Mail) adds a digital signature to your emails, verifying that the content hasn't been tampered with in transit and that the sender is legitimate. DMARC (Domain-based Message Authentication, Reporting, and Conformance) builds on SPF and DKIM, telling receiving servers what to do with emails that fail authentication and providing valuable reports.
Essential authentication checks
SPF record: Ensure it lists all legitimate sending sources and uses a strict policy (e.g., v=spf1 include:_spf.google.com -all). Remove any outdated or unnecessary inclusions, especially those related to services no longer in use, as these can be exploited.
DKIM signature: Verify your DKIM records are correctly published in your DNS and that your sending system is signing emails with the correct key.
DMARC policy: Implement a DMARC record, even starting with a p=none policy to begin receiving reports. These DMARC reports are crucial for identifying unauthorized sending and authentication failures.
This detailed approach to authentication is vital, as it directly signals to Gmail and other mail providers that your domain is secure and that only authorized senders are using it. It's a key component in recovering your email domain's reputation, especially after a serious incident.
Rebuilding sender reputation with Gmail
Once the immediate threat is contained and your authentication is solid, the next phase is to slowly and carefully rebuild trust. This is often referred to as 're-warming' your sending reputation. Instead of immediately resuming full-volume sending, start with highly engaged segments of your audience. Focus on recipients who have recently opened or clicked your emails.
Prioritize sending valuable content to these engaged users. Positive engagement signals, such as opens, clicks, and replies, tell Gmail that your emails are wanted and legitimate. Conversely, sending to disengaged users or spam traps can quickly undo your recovery efforts. Continuously clean your lists, removing inactive subscribers and hard bounces to maintain good list hygiene. This practice will also help recover Gmail email deliverability.
Good list hygiene
Bad list hygiene
Regularly remove inactive subscribers.
Sending to purchased or scraped email lists.
Implement double opt-in for new sign-ups.
Ignoring hard bounces or high spam complaint rates.
Offer clear, easy unsubscribe options.
Sending inconsistent volumes or sporadic large blasts.
Monitor your domain's reputation closely using Google Postmaster Tools. Look for improvements in your domain reputation and lower spam rates. This tool is your primary feedback loop from Google, providing data directly from Gmail about your sending health.
Dealing with blocklists and ongoing monitoring
After a spam attack, your domain or IP might also end up on public blocklists (or blacklists). While Gmail maintains its own internal blocklists, being listed on major public ones can exacerbate your deliverability issues across other providers. Use a blocklist checker to identify if your domain or sending IP has been listed and follow the delisting procedures for each individual blocklist. Keep in mind that removal from a public blocklist doesn't automatically mean Gmail will unblock you, but it's a necessary step.
For specific Gmail issues, there is a bulk sender escalation form. While many report that Gmail rarely responds directly or acts quickly through this channel, it's still worth submitting if you have a legitimate case, such as a clear resolution to a security compromise. Be prepared to provide details about the incident and the steps taken to resolve it.
Finally, ongoing monitoring is essential to prevent future incidents. Regularly check your authentication records, monitor your Google Postmaster Tools dashboard for any dips in reputation or increases in spam complaints, and keep your email lists clean. Proactive monitoring, including blocklist monitoring, allows you to catch issues early, before they escalate into a major block that impacts your core communications.
Views from the trenches
Best practices
Implement a strict DMARC policy with reporting to identify unauthorized sending activity.
Regularly audit your DNS records, especially CNAMEs, to prevent domain hijacking.
Segment your email lists and prioritize sending to your most engaged subscribers first.
Common pitfalls
Neglecting to remove old, unmonitored CNAME records, which can be exploited by malicious actors.
Failing to immediately stop the source of the spam, hindering any reputation recovery efforts.
Sending to unengaged or purchased lists too soon, leading to further damage to your sender reputation.
Expert tips
Focus on gradually rebuilding trust by sending emails that generate positive engagement signals.
Utilize Google Postmaster Tools as your primary resource for Gmail-specific reputation insights.
Don't expect an immediate fix, as reputation recovery takes consistent effort and time.
Expert view
Expert from Email Geeks says that rebuilding trust through gradual re-warming is generally the most effective approach for reputation recovery.
2024-02-07 - Email Geeks
Expert view
Expert from Email Geeks says that while the Google bulk sender form is available, Gmail's direct responses or actions are seldom.
2024-02-07 - Email Geeks
The path forward for your domain
Recovering your domain's reputation after a spam attack and a Gmail block is a journey that demands vigilance, technical precision, and a commitment to best practices. By immediately addressing the security breach, fortifying your email authentication, implementing meticulous list hygiene, and patiently rebuilding trust with engaged recipients, you can systematically improve your sender reputation. Consistent monitoring with Google Postmaster Tools and other resources will be your compass, guiding you back to optimal email deliverability.
Gmail about your sending health.
