Mailgun Report: 18% of Emails Missing the Inbox
Sinch Mailgun's 2026 Email Impact Report reveals 18% of emails fail to reach inboxes due to deliverability gaps and limited AI optimization. What this means for your revenue.
Sarah Mitchell
April 8, 2026
One in five emails never reaches the inbox. That is the core finding from the Sinch Mailgun 2026 Email Impact Report, published on April 8, 2026. Drawing on data from more than 400 billion emails sent in 2025 and a global survey of over 1,200 email senders, the report concludes that nearly 18% of emails fail to reach the inbox, putting up to a fifth of potential ROI at risk for many organizations.
For marketers and growth teams who treat email as a primary revenue channel, that figure is not a rounding error. It is a measurable, addressable performance gap.
What the Data Actually Shows
Despite 78% of survey respondents saying email is critical to business success, the research highlights a growing disconnect between performance and execution, driven by gaps in measurement, deliverability practices, and AI application.
The report introduces new industry benchmarks across 10 high-volume sending sectors, giving businesses a concrete baseline to measure their own inbox placement rates against for the first time at this scale.
The 18% miss rate is not an outlier finding. According to Validity's 2025 Benchmark Report, the global average inbox placement rate sits at 83.5%, meaning roughly 1 in 6 legitimate marketing emails is never seen. The Mailgun figure aligns closely with that broader industry pattern, and both point to a persistent structural problem, not a temporary spike.
In the US and Canada specifically, more than 20% of commercial emails do not reach subscribers' inboxes.
The AI Gap: Adoption Without Impact
One of the more telling findings in the 2026 report concerns AI use. AI adoption is widespread, but its impact remains uneven. Many teams focus on basic use cases such as content generation, while higher-impact applications such as optimization, segmentation, and deliverability remain underutilized. Organizations that use AI more effectively are significantly more likely to report improved email performance.
Kate Nowrouzi, VP of Deliverability at Sinch, put it plainly:
"Using AI to generate content is a good starting point, but it's not where the biggest impact happens. Organizations that apply AI to optimization, segmentation and deliverability are seeing stronger results."
This distinction matters for any team currently using AI primarily to write subject lines or body copy. The lever with the most measurable effect is applying AI to who receives an email, when they receive it, and whether it is routed correctly through the inbox.
