What are good email engagement thresholds for deliverability monitoring?
Matthew Whittaker
Co-founder & CTO, Suped
Published 2 Jun 2025
Updated 19 Aug 2025
6 min read
When I talk about email deliverability, the conversation inevitably turns to engagement thresholds. These aren't just arbitrary numbers, they're critical indicators of how mailbox providers perceive your sending practices. Understanding what constitutes good engagement levels is essential for keeping your emails out of the spam folder and ensuring they reach the inbox.
The challenge is that there isn't a universally fixed benchmark for every metric across all industries or sender types. What's considered acceptable for a transactional email might be completely different for a marketing newsletter. It's a nuanced landscape where context matters as much as the numbers themselves.
My goal is to outline the key engagement metrics I track and provide actionable thresholds that can serve as a starting point for your own deliverability monitoring efforts. These guidelines help me quickly identify potential issues and proactively address them before they escalate.
Core email engagement metrics
To effectively monitor email deliverability, I focus on several core engagement metrics. These include your open rate, click-through rate (CTR), spam complaint rate (also known as abuse rate), and bounce rate. Each of these provides a unique insight into how your audience interacts with your emails.
Mailbox providers, like Google and Outlook, closely observe these metrics to determine your sender reputation and, consequently, your inbox placement. High engagement signals to them that your emails are valuable and desired by recipients, which can lead to better deliverability. Conversely, low engagement can raise red flags.
A consistent decline in these key performance indicators (KPIs) can be an early warning sign of underlying issues, potentially resulting in your emails being filtered into the spam folder or even your domain being added to a blocklist (or blacklist). Proactive monitoring allows you to intervene before your deliverability takes a significant hit.
Metric
Good Threshold
Warning Threshold
Critical Threshold
Open rate
>20%
15-19%
<15%
Click-through rate (CTR)
>2.5%
1.5-2.5%
<1.5%
Spam complaint rate
<0.1%
0.1-0.3%
>0.3%
Bounce rate (overall)
<3%
3-5%
>5%
Unsubscribe rate
<0.3%
0.3-0.5%
>0.5%
Benchmarking and adapting to your audience
While the thresholds I provided are good general benchmarks, it's crucial to remember that they are starting points. The ideal engagement thresholds for your email program are also influenced by your specific audience, the type of content you send, and your sending frequency. For instance, a small, highly niche B2B list might naturally have higher engagement rates than a large B2C promotional list.
For example, B2B email senders often see different engagement patterns compared to B2C. Complaint rates, in particular, tend to be lower in B2B due to the nature of professional communication. This means you might be able to be more aggressive with your thresholds if your primary audience is businesses rather than individual consumers. Gmail enforces a strict complaint rate threshold of 0.3%, which is a hard limit to respect.
Beyond general industry figures, I also recommend establishing a second set of benchmarks based on your own historical performance. By averaging your segment's engagement numbers from the previous year, you can gain a more accurate understanding of what's normal for your specific program. This allows you to monitor how you're performing both within industry averages and against your own past results, highlighting trends that might otherwise go unnoticed.
B2C mailings
Volume: Typically higher sending volumes.
Engagement tolerance: Mailbox providers are often less forgiving of low engagement or high complaint rates.
List hygiene: Requires extremely proactive management to remove unengaged subscribers and bounces.
B2B mailings
Volume: Often lower sending volumes, highly targeted lists.
Engagement tolerance: May tolerate slightly higher bounce rates if lists are frequently updated with new contacts.
Complaint rates: Tend to be lower, but deliverability is still sensitive to negative feedback loops.
Proactive monitoring and deliverability health
Continuous monitoring of these engagement metrics is non-negotiable for maintaining good deliverability. I regularly check platforms like Google Postmaster Tools to gain insights into my domain's performance with major mailbox providers. These tools provide valuable data on spam rates, IP reputation, and more.
If I see consistent dips below my established good thresholds, it signals that I need to investigate. This could involve segmenting my audience more carefully, adjusting sending frequency, or implementing a re-engagement strategy for inactive subscribers. Maintaining a clean and engaged list is foundational to good deliverability.
One area I always pay close attention to is bounce rates, especially hard bounces. High hard bounce rates, particularly in a welcome stream, often point to a significant data acquisition problem. It means that the email addresses you're collecting are invalid or non-existent, which can severely damage your sender reputation and lead to being blocklisted (or blacklisted).
Sender reputation impact
Consistently failing to meet engagement thresholds directly impacts your sender reputation. Mailbox providers interpret low opens, low clicks, and high complaints or bounces as signs that your content is unwanted or that your list quality is poor. This can result in emails being routed to spam or even complete blocklisting. Regularly audit your email lists and engagement to prevent reputation damage.
Beyond basic thresholds
Beyond the basic metrics, I've found it incredibly useful to look at more advanced ratios to get a clearer picture of deliverability issues. For example, focusing on open-to-unsubscribe and open-to-spam ratios can reveal problems that might be masked by seemingly normal overall numbers. This approach helps in understanding what email engagement truly means for your program.
For instance, if your unsubscribe or abuse rates appear normal, but a significant portion of your audience isn't even opening your emails, those per-open ratios can indicate that the active segment of your list has much higher rates of negative feedback than you realize. This can be a strong signal that your list needs deeper segmentation or a re-evaluation of your acquisition methods.
Views from the trenches
Best practices
Monitor open-to-unsubscribe and open-to-spam ratios per mailbox provider for deeper insights.
Compare your current engagement metrics against your historical averages to identify trends.
Segment your audience aggressively based on engagement to prevent low engagement from masking issues.
Overlooking high hard bounce rates in welcome streams, indicating data acquisition issues.
Focusing solely on overall engagement numbers, missing hidden issues within active segments.
Expert tips
Adjust engagement thresholds based on whether your audience is B2C or B2B, as B2B often has lower complaint rates.
If high hard bounces occur in welcome emails, address the root cause of data quality immediately.
Recognize that content, subject lines, and preview text significantly influence engagement metrics.
Expert view
Expert from Email Geeks says abuse numbers often seem out of whack and are typically much lower than commonly assumed. An old rule of thumb for complaint rates being above 0.1% as a risk is now considered too high, as current thresholds are much stricter.
2019-05-23 - Email Geeks
Marketer view
Marketer from Email Geeks says that hard bounce rates should generally be below 4-8% at most. Anything higher, especially in a welcome series, suggests a significant issue with data acquisition that needs immediate attention.
2019-05-23 - Email Geeks
Maintaining your email reputation
Defining good email engagement thresholds for deliverability monitoring is an ongoing process that requires attention to detail and adaptability. While general benchmarks offer a valuable starting point, the most accurate thresholds will always be those that are refined through the consistent analysis of your unique audience behavior and historical performance data.
By diligently monitoring key metrics like open rates, click-through rates, spam complaint rates, and bounce rates, and by digging into more advanced ratios, you can proactively identify issues. This enables you to take corrective action, safeguard your sender reputation, and ultimately ensure your emails consistently land in the inbox.
Google and 
Outlook, closely observe these metrics to determine your sender reputation and, consequently, your inbox placement. High engagement signals to them that your emails are valuable and desired by recipients, which can lead to better deliverability. Conversely, low engagement can raise red flags.
