Why does email domain reputation fluctuate between high and low?
Matthew Whittaker
Co-founder & CTO, Suped
Published 22 Jun 2025
Updated 19 Aug 2025
7 min read
Email domain reputation is a dynamic score that mailbox providers, such as Google and Outlook, assign to your domain based on its sending history. It's like a credit score for your email-sending practices. A high reputation means your emails are likely to reach the inbox, while a low reputation often leads to messages landing in the spam folder or being rejected entirely.
The key word here is dynamic. Unlike a static number, your domain reputation isn't fixed. It constantly shifts, sometimes fluctuating between high and low seemingly without a clear cause. This volatility can be frustrating for email marketers and businesses relying on email for communication, sales, and customer service.
Understanding why these fluctuations occur is crucial for maintaining good email deliverability. It often comes down to a combination of factors related to your sending practices, audience engagement, and technical configurations. Let's explore the common reasons behind these ups and downs.
Engagement and feedback
The primary drivers of domain reputation are recipient engagement and feedback. When recipients interact positively with your emails (opening them, clicking links, replying), it signals to mailbox providers that your content is valuable and desired. Conversely, negative interactions or a lack of engagement can quickly drag your reputation down.
A sudden drop in open rates, for example, especially if you're sending to an unengaged segment of your list, can trigger a decline. This is because low open rates signal to ISPs that your recipients aren't interested. Similarly, a spike in spam complaints, even from a small percentage of your audience, can significantly hurt your standing. Mailbox providers are highly sensitive to user complaints and will quickly take action to protect their users from unwanted mail. Understanding what causes these decreases is the first step in prevention.
Another major factor is your email list hygiene. Sending emails to invalid or nonexistent addresses results in high bounce rates, which negatively impacts reputation. Even worse, hitting spam traps, which are email addresses used to identify spammers, can severely damage your reputation and lead to your domain (or IP) being placed on a blocklist (or blacklist).
Sending practices and content
The volume and frequency of your email sends also play a significant role in reputation fluctuations. Inconsistent sending patterns, such as periods of low activity followed by sudden, large blasts, can trigger spam filters. Mailbox providers prefer a steady, predictable sending volume, as erratic patterns often resemble spammer behavior. How volume and fluctuations affect deliverability is a common challenge for businesses.
Content quality and relevance are equally important. If your emails consistently contain irrelevant content, excessive links, or suspicious formatting, they are more likely to be marked as spam, leading to a drop in reputation. Personalization and segmentation are key to ensuring that your audience receives content that is valuable to them, thereby improving engagement and reducing negative feedback. The email content itself does play a part in sender reputation. Increasing click-through rates is often a good indicator of relevant content.
For domains that send both promotional and transactional emails, using the same domain and IP can be problematic. While transactional emails often have high engagement, promotional blasts (especially to less engaged segments) can drag down the overall reputation, affecting the deliverability of critical transactional messages.
This leads to a sudden drop in deliverability or domain reputation. Careful segmentation and, in some cases, using separate subdomains or IPs for different email streams can help mitigate this risk.
Technical configurations and blocklists
Email authentication protocols like SPF, DKIM, and DMARC are fundamental to building and maintaining a strong domain reputation. Misconfigurations or failures in these protocols can lead to your emails being flagged as suspicious, even if your content and engagement metrics are good. For instance, if your DMARC verification fails, it can directly impact your reputation.
Regularly checking your Google Postmaster Tools and similar dashboards is essential to identify any authentication issues that might contribute to fluctuations. For example, if your DMARC success rate fluctuates, it's a clear signal to investigate your setup.
A p=none policy is a good starting point for DMARC implementation, as it allows you to monitor your email streams without affecting delivery. However, even with this policy, fluctuations can occur if underlying authentication issues are present.
Being listed on an email blocklist (also called a blacklist) is a strong indicator of negative sending practices and will immediately tank your domain's reputation. While some blocklists only list IP addresses, many also list domains. Monitoring these lists and promptly requesting delisting if you find yourself on one is critical for recovery. What happens when your domain is blacklisted can be severe.
IP versus domain reputation
Domain reputation and IP reputation are closely linked but distinct, and understanding their interplay is vital for explaining fluctuations. Your IP reputation is tied to the specific server (or group of servers) sending your emails, while your domain reputation is tied to your brand's domain name.
Domain reputation
Focus: Based on how recipients interact with your emails, including spam complaints and engagement.
Impact: Primarily affects whether your emails land in the inbox or spam folder.
Control: Influenced by content, list quality, sending practices, and authentication.
IP reputation
Focus: Based on the volume and types of emails sent from a specific IP address.
Impact: Affects initial trust and can lead to IP-based blocklisting.
Control: Managed through consistent volume, gradual IP warming, and avoiding spam traps.
If you're using a shared IP, your reputation can be affected by the sending practices of others on that same IP. One bad sender can negatively impact everyone sharing that resource. This can cause your Google Postmaster Tools IP reputation to decrease even if your own sending behavior is good.
Even with a dedicated IP, IP warming can cause fluctuations as mailbox providers learn your sending patterns. Similarly, changing Email Service Providers (ESPs) and using new dedicated IPs can initially lead to a drop in domain reputation as you rebuild trust with ISPs.
Views from the trenches
Best practices
Maintain a consistent sending volume and frequency to build a stable sending history.
Regularly clean your email list by removing unengaged subscribers and invalid addresses.
Segment your audience and personalize content to improve engagement metrics.
Common pitfalls
Sending large, inconsistent email blasts after periods of inactivity.
Ignoring high bounce rates, which indicate poor list hygiene and spam traps.
Sending promotional and transactional emails from the same domain/IP without proper segmentation.
Expert tips
Separate promotional and transactional email streams using distinct subdomains or IPs to protect your core reputation.
Implement DMARC with reporting to gain visibility into your email authentication and delivery, even with a p=none policy.
Focus on nurturing highly engaged subscribers, as their positive interactions significantly boost your domain reputation.
Marketer view
Marketer from Email Geeks says a client had fluctuating reputation due to sending both promotional and transactional emails from the same domain/IP, coupled with inconsistent promotional volumes and list hygiene issues, especially when blasting to their entire 10M+ database without proper segmentation.
2019-10-04 - Email Geeks
Expert view
Expert from Email Geeks says a likely scenario for fluctuating reputation is a mixed bag of traffic that drives the reputation down, followed by days of good traffic that pushes it back up. It is difficult to determine without more specific information about sending practices.
2019-10-04 - Email Geeks
Stabilizing your domain reputation
Domain reputation is a fluid indicator, constantly adjusting based on your recent email sending performance and how recipients interact with your mail. Understanding the underlying causes of its fluctuation is the first step toward stabilizing and improving it.
By focusing on consistent sending practices, maintaining a clean and engaged email list, ensuring robust email authentication, and proactively monitoring your sender metrics, you can minimize volatility. This proactive approach not only helps you navigate the challenges of fluctuating reputation but also builds a more resilient and effective email program.
Google and 
Outlook, assign to your domain based on its sending history. It's like a credit score for your email-sending practices. A high reputation means your emails are likely to reach the inbox, while a low reputation often leads to messages landing in the spam folder or being rejected entirely.
