How to resolve domain blocklisting and improve email reputation?
Matthew Whittaker
Co-founder & CTO, Suped
Published 22 Jun 2025
Updated 19 Aug 2025
5 min read
Getting your domain blocklisted is a challenging experience that can significantly impact your email deliverability. Suddenly, your legitimate emails might start bouncing or landing straight in the spam folder, disrupting critical communications with customers, partners, and employees. It's a frustrating situation that often leaves senders wondering what went wrong and how to fix it.
Many factors contribute to a domain's email reputation, and being added to a blocklist (or blacklist) is a clear sign that your sending practices have fallen short of expectations. The good news is that most blocklist issues are resolvable, and with a strategic approach, you can restore your domain's credibility and ensure your emails reach their intended recipients. It requires understanding the root causes, taking immediate action, and committing to long-term best practices.
Before diving into solutions, it is crucial to understand what domain reputation is and why it matters. Your domain's reputation is essentially a trust score assigned by internet service providers (ISPs) and mailbox providers like Gmail and Outlook. This score determines whether your emails land in the inbox, the spam folder, or are rejected outright. It's based on various factors, including your sending volume, bounce rate, spam complaint rate, engagement metrics, and whether your domain appears on any blocklists (also known as blacklists).
Blocklists are databases of domains and IP addresses known to send spam or malicious emails. When your domain is added to one, it signals to receiving mail servers that your emails might be undesirable. While some blocklists are more influential than others, any listing can negatively affect your deliverability. For a more comprehensive understanding, you can refer to this in-depth guide to email blocklists.
Understanding these factors is the first step in diagnosing and resolving any reputation issues. Here's a quick overview of what impacts your domain's standing:
The first step in resolving any blocklisting issue is to identify where your domain is listed and what the underlying cause might be. While general blocklist checkers can give you an overview, focusing on specific mailbox providers' feedback is often more insightful, particularly for Google and other major ISPs. Tools like Google Postmaster Tools provide valuable insights into your domain and IP reputation, spam rates, and delivery errors directly from Google.
Common culprits for blocklistings include poor list hygiene (sending to old or invalid addresses), high spam complaints, and hitting spam traps. Spam traps are dormant or invalid email addresses used by ISPs and blocklist operators to identify senders of unsolicited mail. Sending to a spam trap is a strong signal that your list acquisition or maintenance practices are problematic. Checking a comprehensive list like the Spamhaus Domain Blocklist can confirm if your domain is listed there.
Common reasons your domain might get blocklisted
Poor list hygiene: Sending to outdated, inactive, or purchased email lists that contain spam traps or invalid addresses.
High complaint rates: Recipients marking your emails as spam, indicating content or sending frequency issues.
Lack of authentication: Missing or misconfigured SPF, DKIM, and DMARC records can lead to emails being seen as illegitimate.
Content issues: Using spammy keywords, suspicious links, or deceptive subject lines.
Sudden volume spikes: Sending a large volume of emails from a new or previously low-volume domain without proper warming up.
Strategies for delisting and reputation improvement
Once you have identified the reasons for your domain's blocklisting, the next step is to initiate the delisting process and work on improving your overall email reputation. It's vital to address the underlying issues first, as simply requesting delisting without fixing the cause will likely lead to a re-listing, making future removal more difficult.
For specific blocklists, you'll typically need to visit their website, search for your domain or IP, and follow their specific delisting instructions. This often involves creating an account, understanding why you were listed, and submitting a request once you've remediated the problem. For broader reputation issues with major providers, the approach is more about consistent, positive sending behavior.
Immediate actions for delisting
Identify blocklists: Use a blocklist checker to find out which specific blocklists your domain is on.
Stop problematic sending: Pause any campaigns or sending practices that led to the listing.
Fix the root cause: Clean your email lists, improve content, or adjust sending frequency.
Submit delisting requests: Follow each blocklist's specific instructions for removal, providing proof of remediation.
Long-term reputation building
Maintain list hygiene: Regularly clean your list to remove unengaged subscribers, invalid addresses, and spam traps.
Monitor engagement: Track opens, clicks, and unsubscribes. Segment or remove unengaged users to improve your overall email reputation.
Implement authentication: Ensure your SPF, DKIM, and DMARC records are correctly configured and enforced.
Warm up new IPs/domains: Gradually increase sending volume from new sending infrastructures to build trust.
Remember that improving your email domain and IP reputation is a marathon, not a sprint. Consistency and adherence to best practices will yield the best results over time.
Maintaining a healthy email program
Prevention is always better than cure. To avoid future blocklistings and maintain a robust email reputation, integrate these practices into your ongoing email strategy. Continuous monitoring and adaptation are key.
Proactive reputation management
Implement strong authentication: Ensure your SPF, DKIM, and DMARC records are correctly configured. This verifies your sending identity and builds trust. You can learn more in our simple guide.
Monitor your deliverability: Regularly check your domain's reputation using tools like Google Postmaster Tools and perform blocklist monitoring.
Practice consent-based sending: Only send emails to recipients who have explicitly opted in.
Provide easy unsubscribe options: Make it simple for recipients to opt out, reducing spam complaints.
Segment and personalize: Send relevant content to specific audience segments to boost engagement.
A key technical step is to ensure your DMARC monitoring is in place. DMARC reports provide invaluable feedback on how your emails are being authenticated and delivered, helping you spot issues early. Here's a basic example of a DMARC record:
This record tells receiving servers how to handle emails that fail DMARC authentication and where to send aggregate and forensic reports, which are crucial for diagnostics.
Views from the trenches
Best practices
Prioritize addressing reputation issues with major mailbox providers like Google over less influential blocklists.
Focus on sending highly engaging content that encourages positive recipient interactions to improve your sender reputation.
Implement robust list hygiene practices to remove old, unengaged, or problematic email addresses.
Continuously monitor your email list segmentation to ensure you are not sending to stale or unverified contacts.
Common pitfalls
Over-relying on delisting tools without first identifying and resolving the root cause of the listing.
Requesting delisting from a blocklist without making necessary changes to sending practices, leading to re-listing.
Ignoring the importance of engagement metrics, which are crucial signals for mailbox providers.
Sending large blasts to entire lists without proper segmentation or re-engagement strategies.
Expert tips
Utilize Google Postmaster Tools to gain insights into your domain's reputation with Google and identify potential issues.
Understand the specific criteria of each blocklist before attempting delisting, as some are less impactful than others.
Systematically identify the root cause of deliverability issues by analyzing bounce rates, spam complaints, and engagement.
Educate your internal teams on email best practices to foster a culture of deliverability awareness.
Marketer view
A marketer from Email Geeks says that being listed on SORBS SPAM alone might not significantly impact deliverability, as it's not as widely referenced by ISPs.
August 24, 2021 - Email Geeks
Expert view
An expert from Email Geeks says it is more critical to address issues with major mailbox providers like Google than smaller blocklists like SORBS.
August 24, 2021 - Email Geeks
The path to better email deliverability
Resolving domain blocklisting and improving your email reputation might seem daunting, but it's a manageable process with the right strategy. It involves a combination of immediate remedial actions and long-term commitment to email best practices. By understanding how reputation works, identifying the root causes of any issues, and diligently implementing solutions, you can restore your domain's health.
Remember that consistent monitoring, rigorous list hygiene, proper authentication, and sending valuable content to engaged subscribers are the cornerstones of excellent deliverability. Investing time in these areas will not only help you recover from blocklistings but also build a resilient email program that ensures your messages consistently reach the inbox.
Spamhaus
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Cisco
NoSolicitado
URIBL
abuse.ro
ALPHANET
Anonmails
Ascams
BLOCKEDSERVERS
Calivent Networks
EFnet
JustSpam
Kempt.net
NordSpam
RV-SOFT Technology
Scientific Spam
Spamikaze
SpamRATS
SPFBL
Suomispam
System 5 Hosting
Team Cymru
Validity
www.blocklist.de Fail2Ban-Reporting Service
ZapBL
2stepback.dk
Fayntic Services
ORB UK
technoirc.org
TechTheft
Gmail and 
Outlook. This score determines whether your emails land in the inbox, the spam folder, or are rejected outright. It's based on various factors, including your sending volume, bounce rate, spam complaint rate, engagement metrics, and whether your domain appears on any blocklists (also known as blacklists).
Google and other major ISPs. Tools like Google Postmaster Tools provide valuable insights into your domain and IP reputation, spam rates, and delivery errors directly from Google.
