One of our values at Kit is to work in public. We strive for transparency, which is why we share information that is typically kept private, such as our finances.
One commonly asked question by creators looking for a new email marketing platform is, “How is your email deliverability?”
Here is our monthly deliverability report to answer that question:
If you missed previous Deliverability reports, you can check them out below:
In May, Kit sent over 1.3 billion messages (1,333,560,723 to be exact).
When messages are sent, they can be delivered or they can bounce. For more details on how email deliverability operates, check out our blog post here. But for a little TLDR- The more messages delivered, the better!
It is inevitable for some messages to bounce due to invalid addresses, full mailboxes, etc., but a good delivery rate indicates healthy deliverability for Kit. We consider a system-wide delivery rate of 98% and above to be very healthy.
In May, our system-wide delivery rate was 99.72%.

This high delivery rate indicates a healthy reputation for Kit, which gives our customers a solid foundation for their email deliverability. To get even more detailed about how well we’re performing, it helps filter down by mailbox provider.
Here are the top 5 domains Kit sends to in terms of volume:
1. Gmail.com
802 million messages
Delivery rate: 99.93%
2. Yahoo.com
133 million messages
Delivery rate: 99.94%
3. Hotmail.com
100 million messages
Delivery rate: 99.86%
4. AOL.com
30 million messages
Delivery rate: 99.97%
5. Outlook.com
14 million messages
Delivery rate: 99.88%
The average open rate of all emails sent through Kit was 29.2%.
Senders often ask how their open rates stack up to others. The truth is, open rates can vary greatly depending on your industry and audience type (B2B vs. freemail addresses, for example). However, here’s a general scale you can use to measure your performance:

I talk more about open rates and why they aren’t always reliable in this article.
The average click rate across Kit accounts was 5.61%.
We calculate click rate by dividing the number of subscribers who clicked a link by the total number of subscribers who received the email.
Similarly, the average click-to-open rate was 16.63%. This is calculated by dividing the number of subscribers who clicked a link by the number of subscribers who opened the email.
Our system-wide complaint rate remained over 10x lower than the industry standard
A complaint is when a subscriber marks a message as spam. An elevated complaint rate is a signal that the sender’s quality of mail isn’t good. We have a team dedicated to ensuring that the recipients want the mail sent from Kit.
In the email industry, a complaint rate of less than 0.1% is seen as healthy. Kit’s complaint rate in May was 0.0047%, which speaks to the high quality of mail sent by our customers and the healthy reputation of our infrastructure.
Deliverability tip of the month:
While we’ve always shared that open rates are an unreliable metric, Apple’s latest announcement will make them even more unpredictable. It’s time for senders to start measuring other metrics to determine engagement if they haven’t already.
Senders should start to think about how they can drive other engagement metrics, such as clicks, to determine which subscribers are actively engaging with your emails. For newsletters, this might look like including less content in your email than you usually would, and instead include a “Read more” link for your subscribers to view the full content. For other senders, this might look like adding a “like” icon to your email and encouraging subscribers to click it to give you feedback.
Industry news and Kit updates
The Deliverability Defined Podcast

We’ve been having so much fun releasing more episodes of our deliverability podcast! Here are the episodes we released in May:
- Why do emails bounce?
- How to recover from an email fail
- A day in the life of a deliverability expert
- Things to check before you click “send”