How to improve email sender reputation after a low period?
Michael Ko
Co-founder & CEO, Suped
Published 21 Apr 2025
Updated 18 Aug 2025
7 min read
Email sender reputation is the backbone of your email program. It's how internet service providers (ISPs) like Gmail and Outlook determine if your emails are legitimate and should land in the inbox, or if they're spam. When your sender reputation takes a hit, it can feel like a deliverability nightmare, with emails consistently landing in spam folders or being outright rejected.
A low period in your sender reputation isn't just a minor inconvenience; it's a critical issue that can severely impact your communication effectiveness and business operations. It signals to mailbox providers that your sending practices might be problematic, leading to reduced inbox placement and wasted marketing efforts. The good news is that reputation isn't permanently fixed, and there are concrete steps you can take to turn things around.
Rebuilding a low sender reputation requires a systematic approach, patience, and diligent monitoring. It's a journey, not a quick fix. I'll guide you through the essential steps to understand why your reputation declined, how to implement crucial technical fixes, refine your content and audience strategy, and gradually re-establish trust with mailbox providers.
Understanding the impact of a low reputation
Before you can begin to improve your sender reputation, you need to understand what caused it to drop in the first place. Common culprits include high bounce rates, an influx of spam complaints, low engagement from recipients, or even getting listed on an email blacklist (or blocklist). Identifying the root cause is crucial for effective remediation.
Mailbox providers use various signals to assess your reputation. These include your IP address reputation, domain reputation, and content quality. If your emails start consistently landing in the spam folder or you notice a sudden drop in deliverability, it's a clear sign that your reputation has suffered. Checking your Google Postmaster Tools will provide valuable insights into your domain's health and reputation metrics.
Being on an email blacklist (also known as a blocklist) can significantly hinder your email deliverability. These lists track IP addresses and domains associated with sending unwanted mail. If your domain finds its way onto one, it signals to receiving mail servers that your emails should be treated with suspicion, often leading to immediate rejection or redirection to the spam folder. Understanding what happens when your domain is blocklisted is a crucial first step in mitigation.
Foundation for recovery: technical setup
The technical foundation of your email sending is paramount. Ensuring your domain is properly authenticated is a non-negotiable step to improve a low sender reputation. This involves setting up and correctly configuring SPF, DKIM, and DMARC records.
SPF (Sender Policy Framework) specifies which mail servers are authorized to send email on behalf of your domain. DKIM (DomainKeys Identified Mail) adds a digital signature to your emails, verifying that the message hasn't been tampered with and truly comes from your domain. DMARC (Domain-based Message Authentication, Reporting, and Conformance) builds on SPF and DKIM, providing instructions to receiving servers on how to handle emails that fail authentication, and offering valuable reporting. A simple guide to DMARC, SPF, and DKIM can help clarify their roles.
If you're unsure about your current setup, consider using a DMARC record generator or a dedicated DMARC monitoring solution to gain visibility into your email authentication performance. This is a foundational step in demonstrating trustworthiness to mailbox providers.
Once the technical groundwork is solid, focus shifts to your email list and content. A clean, engaged list is vital for a healthy sender reputation. Regularly cleaning your email list to remove inactive subscribers, invalid addresses, and particularly, spam traps, is critical. Spam traps are email addresses used by ISPs to identify senders who are not maintaining their lists, and hitting them can severely damage your reputation. Learn more about spam traps and how they work.
Prioritize organic list growth. Encourage users to explicitly opt-in to your emails. Double opt-in processes can further ensure that your subscribers genuinely want to receive your communications, significantly reducing the likelihood of spam complaints. Additionally, segmenting your audience and tailoring your content to their interests can boost engagement, a key factor in improving your reputation.
The content of your emails also plays a significant role. Ensure your subject lines are clear and avoid spammy keywords or excessive capitalization. Provide valuable content that your audience expects, and make it easy for recipients to unsubscribe if they wish. A prominent and functional unsubscribe link can prevent frustrated recipients from marking your emails as spam.
Content and list hygiene best practices
List cleaning: Regularly remove inactive subscribers and invalid email addresses to reduce bounce rates.
Opt-in process: Implement double opt-in to ensure engaged subscribers and reduce spam complaints.
Content relevance: Send valuable and personalized content that aligns with subscriber expectations.
Unsubscribe options: Make the unsubscribe process clear and easy to find.
The recovery process: warming up and monitoring
After addressing the foundational and content issues, the recovery phase begins with a careful email warm-up. If your reputation has been low, suddenly sending large volumes of emails will only worsen the situation. Instead, start by sending small volumes to your most engaged subscribers and gradually increase your sending volume over time. This approach, known as email warming, helps rebuild trust with ISPs. HubSpot's article on improving email deliverability elaborates on this process.
During this period, meticulous monitoring of your email performance metrics is non-negotiable. Pay close attention to your open rates, click-through rates, bounce rates, and crucially, your spam complaint rate. A high spam complaint rate is a major red flag for ISPs. Aim to keep this below 0.1%. Consistently positive engagement signals to mailbox providers that your emails are valued by recipients. This careful process is key to a successful domain reputation recovery.
Regularly check if your domain or IP address is listed on any blocklists (or blacklists). Many blocklist checking tools are available. Promptly request delisting if you find yourself on one, but only after you have addressed the underlying issues that led to the listing. Ignoring a blocklist entry will only prolong your reputation issues and prevent your emails from reaching the inbox.
Another powerful way to assess your standing is to simply send yourself emails using different email providers. This easy and efficient way offers immediate insight into whether your emails are landing in the inbox or spam.
Before: low reputation
Email placement: Messages consistently land in spam or are rejected.
Bounce rates: High numbers of hard and soft bounces.
Spam complaints: Elevated complaint rates from recipients.
Engagement: Low open and click-through rates.
After: improving reputation
Email placement: Emails consistently reach the inbox.
Bounce rates: Significant reduction in bounce rates.
Spam complaints: Complaint rates are minimal, ideally below 0.1%.
Engagement: Higher open and click-through rates indicate user interest.
Metric
Target for healthy reputation
Impact of poor metric
Spam complaint rate
Below 0.1%
High rates lead to spam folder delivery.
Bounce rate
Below 2-5%
Excessive bounces damage IP and domain reputation.
Open rate
Industry dependent, but strong engagement is key
Low opens signal disinterest, impacting reputation negatively.
Unsubscribe rate
Below 0.5%
High unsubscribes can point to irrelevant content or frequency issues.
Views from the trenches
Best practices
Maintain a consistent sending schedule to build predictable sending patterns and avoid erratic spikes.
Segment your lists rigorously and target engaged subscribers first during recovery.
Prioritize sending valuable content that resonates with your audience to boost engagement.
Common pitfalls
Sending large volumes immediately after a reputation drop, which can worsen the situation.
Ignoring bounce messages and continuing to send to invalid or inactive addresses.
Not regularly monitoring sender reputation metrics or blocklist status.
Expert tips
Consider a phased approach, starting with your most engaged segments and slowly expanding.
Utilize re-engagement campaigns to identify and remove truly inactive subscribers.
Ensure your authentication records (SPF, DKIM, DMARC) are always correctly configured.
Marketer view
Marketer from Email Geeks says they started with a small group of 50 engaged users and gradually increased by 15% daily, reaching 20,000 sends in 30 days, which helped improve their reputation despite a temporary spam spike.
2025-06-04 - Email Geeks
Marketer view
Marketer from Email Geeks mentioned that it's challenging to move the reputation needle, underscoring the effort required for recovery.
2025-06-04 - Email Geeks
Restoring your email sending trust
Rebuilding email sender reputation after a low period is a comprehensive process that demands attention to detail across technical setup, list hygiene, content strategy, and sending practices. It's a testament to patience and persistence, as immediate results are rare. However, by systematically addressing the underlying issues and committing to best practices, you can gradually restore trust with mailbox providers and ensure your emails reach their intended audience.
The key is to remember that your sender reputation is dynamic, constantly influenced by your sending behavior and recipient engagement. By focusing on delivering value to an engaged audience and maintaining a robust technical foundation, you can not only recover from a low period but also build a resilient and high-performing email program for the long term.
Gmail and 
Outlook determine if your emails are legitimate and should land in the inbox, or if they're spam. When your sender reputation takes a hit, it can feel like a deliverability nightmare, with emails consistently landing in spam folders or being outright rejected.
