How important is IP reputation versus domain reputation, especially for B2B senders with low engagement and emails going to spam?
Matthew Whittaker
Co-founder & CTO, Suped
Published 27 Jul 2025
Updated 17 Aug 2025
8 min read
For B2B senders, navigating the complexities of email deliverability can be challenging, especially when dealing with low engagement and emails consistently landing in spam folders. A common question arises: how much does IP reputation truly matter compared to domain reputation? While both are components of your overall sender reputation, their relative importance has shifted over time, with domain reputation often taking precedence in modern email filtering.
The digital landscape of email delivery is constantly evolving. What was once heavily dependent on the sending IP's history is now a more nuanced evaluation, taking into account many signals, including user interaction and authentication. This shift particularly impacts B2B senders, where even small changes in deliverability can have significant business implications. Understanding this dynamic is crucial for ensuring your critical business communications reach their intended recipients.
The foundation of email sender reputation
Sender reputation is essentially how internet service providers (ISPs) and mailbox providers (MBPs) perceive your sending practices. It’s a trust score that dictates whether your emails land in the inbox, spam folder, or are rejected entirely. This score is a composite of various factors, but at its core are two main components: IP reputation and domain reputation.
IP reputation is tied to the numerical address of the server sending your emails. A good IP reputation means that the IP has a history of sending legitimate, desired mail. Conversely, an IP with a poor reputation has likely been associated with spam or unwanted mail, leading to blocklistings (blacklistings) and delivery issues. This is especially true for shared IP pools, where the actions of one sender can negatively affect others using the same IP. For instance, if an IP address is on a blocklist, it can significantly impact deliverability. You can learn more about what happens when your IP gets blocklisted.
Domain reputation, on the other hand, is associated with your sending domain (the part after the "@" in your email address). This is built on the history of emails sent from that specific domain, including user engagement, spam complaints, and adherence to email authentication protocols like SPF, DKIM, and DMARC. Many modern email filtering systems, including those used by Google and Microsoft, heavily weigh domain reputation because it's directly linked to the brand sending the email. A detailed understanding of these protocols can be found in a simple guide to DMARC, SPF, and DKIM.
Domain reputation: The modern priority for B2B senders
For B2B senders, domain reputation has become increasingly critical. Unlike consumer-facing mail, B2B emails often have lower engagement rates by nature, as they might be transactional, informational, or part of a longer sales cycle. In this environment, where engagement signals can be sparse, a strong domain reputation signals trustworthiness to sophisticated enterprise filtering solutions like Proofpoint and Mimecast, as well as Microsoft EOP and Google Workspace.
These advanced filters prioritize domain reputation because it offers a more stable and reliable indicator of sender legitimacy over time. Even if you're sending from a dedicated IP, a bad domain reputation will likely result in emails landing in spam. As one industry expert states, "Domain reputation is the primary factor driving B2B email deliverability" (Source: Allegrow). More on this topic is available in the article on how domain reputation affects email deliverability compared to IP reputation.
The focus on domain reputation means that consistent, quality sending practices are paramount. This includes maintaining clean email lists, sending relevant content, and ensuring strong authentication. A significant number of spam reports or low engagement can quickly harm your domain's standing, even if your IP is clean. This becomes particularly evident in scenarios where emails are going to spam despite efforts to warm up an IP. The general consensus is that getting your mail out of the spam folder is the first priority.
IP reputation factors
Shared IP risks: Senders in shared IP pools (especially with low volume) can suffer from the poor sending practices of other users on the same IP.
Volume threshold: Establishing a reliable IP reputation, particularly with mailbox providers like Google, often requires significant sending volume, sometimes more than 2,000 unique emails daily.
Less emphasis by some MBPs: Some major mailbox providers are placing less emphasis on IP reputation, shifting their focus more towards domain behavior and user engagement.
Blocklists: Your IP being listed on a blocklist (or blacklist) will significantly impact deliverability across many providers.
Domain reputation factors
User engagement: Opens, clicks, replies, and marking emails as "not spam" all contribute positively to your domain's reputation. Low engagement is a significant negative signal.
Spam complaints: High complaint rates are a strong indicator of unwanted mail and severely damage domain reputation.
Authentication: Proper implementation of SPF, DKIM, and DMARC demonstrates authenticity and helps build trust with mailbox providers.
Content quality: Irrelevant or poorly formatted content can lead to negative user interactions and lower domain reputation, pushing emails to spam.
Addressing low engagement and spam for B2B
When B2B emails consistently land in spam, it's a clear sign that your sender reputation, specifically your domain reputation, is suffering. Low engagement is a key indicator to mailbox providers that your emails are either unwanted or irrelevant. For B2B senders, who often deal with smaller, highly targeted lists, every interaction counts.
To combat low engagement and high spam rates, the emphasis must shift from just the technical aspects of IP management to the qualitative aspects of your email program. This includes:
Audience segmentation: Ensure your messages are highly targeted to recipients who genuinely want to receive them.
Content relevance: Provide valuable, engaging content that encourages opens, clicks, and replies. Irrelevant content is a primary driver of low engagement.
List hygiene: Regularly clean your email lists to remove inactive subscribers, hard bounces, and especially spam traps. Sending to unengaged or invalid addresses signals poor sending practices.
Clear calls to action: Make it easy for recipients to engage with your emails, whether through clicks, replies, or unsubscribing gracefully.
Even with low volume, consistent positive engagement signals will build a strong domain reputation. Conversely, sending 20,000 emails with poor engagement will quickly tank your reputation. This is where the challenge lies for B2B senders with naturally lower engagement, as outlined in why your emails are going to spam in 2024 and how to fix it.
The spiral of low engagement
When B2B emails experience low engagement rates, mailbox providers interpret this as a signal that your content is not valued by recipients. This can lead to your domain's reputation deteriorating rapidly.
A declining domain reputation results in more emails being directed to the spam folder, further reducing engagement and creating a negative feedback loop.
This issue is often compounded for low-volume B2B senders, as each negative interaction carries more weight relative to the total volume.
Focus on content quality and list health.
The shared vs. dedicated IP dilemma for B2B
A common consideration for senders facing deliverability issues, particularly with a poor IP reputation in a shared pool, is whether to switch to a dedicated IP address. While a dedicated IP provides more control over your sending reputation by isolating you from other senders, it also means you bear full responsibility for building and maintaining that reputation. For B2B senders with low daily volumes (e.g., under 5,000, or even just 100 emails to a specific MBP), establishing a robust IP reputation on a new dedicated IP can be a slow process.
Some experts suggest that a daily volume of 100+ emails to unique Gmail users might be enough to see basic reputation data in Google Postmaster Tools. However, significant volume (perhaps 2,000+ daily) is often needed to truly establish a strong, independent IP reputation. If your current shared IP pool has a "crappy IP rep," moving to a dedicated IP might seem like a quick fix, but it's only beneficial if paired with a strong focus on domain reputation and positive user engagement. In many cases, if your domain reputation is already bad, simply changing the IP won't solve the underlying problem.
Ultimately, whether on a shared or dedicated IP, the principles of good sending remain the same: send mail that recipients want. Mailbox providers are sophisticated enough to look beyond just the IP address to the behavior of the sending domain. They assess whether the mailstream is genuinely desired by recipients, which is reflected in your domain's reputation. You can gain more insights by checking how your sending practices impact domain reputation and deliverability.
Views from the trenches
Best practices
Prioritize domain health: Focus intensely on maintaining a high domain reputation through positive recipient engagement, rather than solely on IP reputation.
Implement authentication: Ensure your domain has proper SPF, DKIM, and DMARC records to prove authenticity and build trust.
Monitor user feedback: Actively track spam complaints, unsubscribe rates, and engagement metrics to identify and address issues promptly.
Segment your audience: Send highly relevant emails to specific, engaged segments of your audience to maximize positive interactions.
Common pitfalls
Ignoring domain reputation: Overemphasizing IP reputation while neglecting poor domain health leads to emails consistently hitting the spam folder.
Sending to unengaged lists: Continuing to send emails to recipients who rarely open or click signals low value to mailbox providers, harming your sender score.
Lack of authentication: Failing to properly configure SPF, DKIM, and DMARC can cause emails to fail authentication checks, negatively impacting deliverability.
Volume over quality: Believing that sending high volumes of email will automatically build reputation, even if content is poor or recipients are unengaged.
Expert tips
Content is king: The most crucial aspect is sending mail that recipients genuinely want to receive; this drives positive user behavior and reputation.
Understand mailbox provider algorithms: Recognize that each mailbox provider has unique, often undisclosed, algorithms for reputation, making direct control challenging.
Leverage available tools: Use Google Postmaster Tools for Gmail insights and external services like Cisco Talos Intelligence for IP blocklist checks.
Address the root cause: If emails are going to spam, the fundamental problem is usually with the email program itself, requiring a holistic change, not just minor adjustments.
Expert view
Expert from Email Geeks says: "Nobody really knows precisely how Gmail measures IP reputation, and anyone claiming to know for sure is likely exaggerating. Google’s system is complex, and consistency in sending patterns is a good general objective."
August 29, 2024 - Email Geeks
Marketer view
Marketer from Email Geeks says: "I've heard that establishing IP reputation typically requires significant volume, often 2,000 or more messages daily, while 100+ per day might suffice for spam rate and domain reputation data in tools like Google Postmaster Tools."
August 29, 2024 - Email Geeks
What matters most for B2B senders
For B2B senders grappling with low engagement and emails ending up in spam, the takeaway is clear: domain reputation is paramount. While IP reputation still plays a role, especially in avoiding major blocklists (blacklists) and with certain mailbox providers, the overwhelming trend is for MBPs to prioritize signals tied directly to your domain and, more importantly, user behavior. If your domain's reputation is poor, simply changing your IP will not solve your deliverability challenges.
Your focus should be on cultivating a mailstream that recipients genuinely want to receive. This involves rigorous list hygiene, highly relevant content, consistent sending patterns, and robust email authentication. By prioritizing these elements, you build a positive domain reputation that transcends the nuances of IP addresses and leads to consistent inbox placement for your critical B2B communications.
Google and 
Microsoft, heavily weigh domain reputation because it's directly linked to the brand sending the email. A detailed understanding of these protocols can be found in a simple guide to DMARC, SPF, and DKIM.
Proofpoint and 
Mimecast, as well as 
Google Workspace.
