How to improve email IP and domain reputation and what to audit for deliverability?
Matthew Whittaker
Co-founder & CTO, Suped
Published 29 Jul 2025
Updated 14 Aug 2025
9 min read
Summary
Email IP and domain reputation are crucial for successful email delivery. A poor reputation can lead to messages being blocked, sent to spam folders, or experiencing significant delays, impacting critical business communications. This page explores how to improve and maintain a healthy email reputation, outlining key audit points for deliverability.
Key findings
Reputation Impact: A history of sending marketing emails from an operational IP can severely damage its reputation, even after correction.
Authentication Gaps: Failing DKIM signatures are a significant barrier to improving domain reputation, as they undermine trust with mailbox providers. Correct authentication (SPF, DKIM, DMARC) is foundational.
Hosting Environment: The choice of email hosting provider and whether you are on a dedicated or shared IP address can heavily influence your deliverability.
Audit Necessity: A comprehensive email deliverability audit is essential to identify underlying issues and create a roadmap for improvement. This includes reviewing technical setups, sending practices, and policy adherence. Read more about improving your sender reputation in this Mailgun article.
Dedicated vs. Shared IPs: Assess whether a dedicated IP address is necessary for your operational email, especially if shared IPs are negatively impacting your reputation due to other senders' practices.
Email Host Reliability: Evaluate your current email hosting provider, particularly if they are not reliably supporting essential features like DKIM signing or maintaining valid TLS certificates for their own services.
Migration Strategy: Consider migrating email hosting to a more robust provider if current issues persist and cannot be resolved with the existing setup.
Internal Communication: Foster open communication with your technical team (e.g., CTO) to understand the full scope of your email infrastructure and gain their support for necessary changes.
Consistent Monitoring: Regularly monitor Google Postmaster Tools and DMARC reports to track reputation changes and identify potential issues early.
What email marketers say
Email marketers often face the challenge of managing sender reputation, especially when past practices have inadvertently harmed their deliverability. Their experiences highlight the practical impact of technical configurations and the importance of clear segmentation between different email streams. They frequently grapple with diagnosing issues when direct error messages are not readily available and seek actionable advice to restore a healthy sending reputation.
Key opinions
Diagnostic Challenges: Marketers frequently find it difficult to pinpoint the exact cause of low reputation without specific bounce messages or error codes, making improvement efforts challenging.
Postmaster Tools: Google Postmaster Tools is a key resource for self-diagnosing IP and domain reputation, but sometimes the recovery process can be slow.
Internal vs. Marketing: There's often confusion or historical misuse where corporate operational emails and marketing emails might share the same IP or domain, negatively impacting the former.
Authentication Importance: Even marketers acknowledge that authentication standards like DKIM, SPF, and DMARC are fundamental, though understanding their intricacies can be daunting. A comprehensive guide to sender reputation can be a valuable resource.
Key considerations
Separate Mail Streams: It is crucial to use different IPs and potentially subdomains for operational and marketing emails to prevent reputation bleed.
DKIM Fix: Prioritize fixing any broken DKIM signing, as it is essential for building and maintaining domain reputation.
Comprehensive Audit: Undertake a full email audit to understand every aspect of the email sending setup, from technical configurations to sending practices.
Reply-To Address: The choice of whether to match the 'From' and 'Reply-To' addresses should be based on reply handling strategy, not deliverability concerns, as it generally has no impact on inbox placement.
Understanding Headers: Learn to interpret email headers to gain deeper insights into email routing, authentication results, and potential issues that might not be obvious elsewhere.
Marketer view
Marketer from Email Geeks reports that their corporate email IP reputation is currently ranked as low on Google Postmaster Tools. This is despite the IP being used primarily for internal company communications, suggesting a significant historical issue. While the domain's reputation is showing signs of improvement, moving from low to medium, the persistent low IP score remains a concern. They also note a lack of specific bounce messages or error codes, making diagnosis challenging.
01 Oct 2019 - Email Geeks
Marketer view
Marketer from Email Geeks questions the reason for continued low reputation, stating that two months after correcting email sending practices, their IP reputation has not improved. This highlights the prolonged challenge of rehabilitating a damaged IP reputation. They are seeking standard methods to improve IP reputation, indicating a need for clear, actionable strategies beyond simply stopping the problematic sending.
01 Oct 2019 - Email Geeks
What the experts say
Email deliverability experts highlight the intricate interplay between IP and domain reputation, stressing the importance of proper authentication and careful management of sending infrastructure. They emphasize that while technical fixes are crucial, a holistic audit of sending practices, list hygiene, and compliance is equally vital. Their insights often involve dissecting email headers for diagnostic purposes and understanding the nuances of shared versus dedicated IPs.
Key opinions
DKIM's Role: DKIM is essential for building domain reputation, not just for security and deliverability. Without it, improving domain trust is significantly harder.
Email Hosting Scrutiny: An email host that does not offer or reliably support DKIM should be a concern, as it indicates a lack of fundamental email best practices.
Comprehensive Audit: A full audit of all email streams, domains, and IP addresses is recommended to gain a complete picture of sending practices and identify hidden issues.
Shared IP Risks: Using shared IP addresses, while common for smaller operations, carries the risk of reputation being negatively affected by other senders using the same IP. Understanding shared IP dynamics is key.
Policy and Compliance: Beyond technical settings, understanding how addresses are collected, compliance with local laws (like GDPR, see GDPR's impact), FBLs, and abuse address functionality are crucial for sustained deliverability.
No Cold Emailing: Sending unsolicited or cold emails from any IP, especially operational ones, is detrimental to reputation.
Key considerations
Technical Foundations: Ensure correct SPF, DKIM, and DMARC configurations. Verify rDNS is set, HELO values are consistent, and MailFrom addresses are correctly configured.
MTA Configuration: Audit Mail Transfer Agent (MTA) settings for correct sending limits, deferred mail handling, retry periods, and how permanent rejections are managed to ensure list hygiene.
Reputation Tools: Utilize tools like GlockApps for seedlist testing, Cisco Talos for comprehensive threat intelligence, and SenderScore for a numerical reputation score. Additionally, regularly check blocklists to ensure your IP or domain is not listed.
Email Hosting Provider: Consider migrating to a reputable email hosting provider (e.g., G Suite, Microsoft Exchange) if your current provider exhibits issues with fundamental email functions like DKIM signing or TLS certificates. An article on fixing and improving IP reputation can be helpful.
Expert view
Expert from Email Geeks explains that getting DKIM (DomainKeys Identified Mail) working correctly is absolutely essential for building and maintaining domain reputation. This authentication method proves that an email was authorized by the domain owner, significantly increasing trust with mailbox providers. Without a valid DKIM signature, emails are more likely to be flagged as suspicious or spam, regardless of other sending practices, making it a critical component for deliverability.
01 Oct 2019 - Email Geeks
Expert view
Expert from Email Geeks advises that cold emails are inherently problematic for sender reputation, and any IP used for operational email should strictly avoid such practices. Unsolicited bulk email sending can quickly lead to blocklistings and a severely damaged IP reputation, affecting all legitimate traffic from that IP. They suggest that a thorough audit is needed to identify exactly what types of emails are being sent from each IP address and to whom, ensuring that no unauthorized or detrimental sending activities are occurring.
01 Oct 2019 - Email Geeks
What the documentation says
Official documentation and research often underscore the foundational role of email authentication (SPF, DKIM, DMARC) in establishing sender credibility. They detail the mechanisms by which mailbox providers assess IP and domain reputation, emphasizing adherence to established protocols and best practices to ensure messages are not flagged as spam. Documentation typically provides guidelines for proper configuration, data interpretation from postmaster tools, and strategies for maintaining a healthy sending ecosystem.
Key findings
Authentication Standards: SPF, DKIM, and DMARC are fundamental protocols for email authentication, crucial for verifying sender identity and preventing spoofing. Proper configuration of these significantly impacts deliverability and sender reputation.
Reputation Metrics: Sender reputation is influenced by various metrics including bounce rates, spam complaint rates, email volume, and consistent sending patterns. Mailbox providers use these to determine trustworthiness.
List Hygiene: Regular validation and cleaning of email lists to remove invalid addresses and spam traps are essential for maintaining a positive reputation and reducing hard bounces.
Postmaster Tools: Tools like Google Postmaster provide valuable insights into domain and IP reputation, spam rates, and other critical deliverability metrics, enabling proactive management. A Twilio article on checking sender reputation can offer further insight.
Key considerations
Gradual Warmup: When using new IPs or domains, a gradual warmup process is recommended to build reputation slowly and establish trust with ISPs.
Content Quality: Email content should be relevant, personalized, and free of spammy characteristics to encourage engagement and reduce complaints.
Feedback Loops: Signing up for ISP feedback loops allows senders to be notified of spam complaints, enabling prompt removal of disengaged recipients.
Compliance: Adherence to industry regulations and local privacy laws (e.g., CAN-SPAM, GDPR) is non-negotiable for maintaining a good sender reputation.
Technical article
Documentation from Mailgun states that regularly verifying your email list is a critical step to improve and protect sender reputation. This process involves purging invalid addresses, spam traps, and disengaged subscribers from your lists. The direct benefit of this practice is a significant reduction in bounce rates, which are a key indicator of list quality and a major factor influencing how ISPs perceive your sending practices. Lowering your bounce rate directly contributes to a higher sender reputation.
22 Jun 2024 - Mailgun Blog
Technical article
Documentation from Twilio highlights that email sender reputation directly influences email deliverability. A strong reputation ensures that emails are consistently delivered to the inbox, while a poor one can result in messages being diverted to spam folders or blocked entirely. They emphasize the importance of using various tools and tips to check and monitor sender reputation, as understanding these metrics is the first step toward improving overall email deliverability and ensuring your communications reach their intended audience.
