Definition
Email acceptance rate is the ratio of emails accepted by receiving mail servers to the total number of emails attempted during a send. While closely related to delivery rate, acceptance rate specifically measures whether the recipient server accepted the message at the SMTP level, before any inbox placement or spam filtering occurs.
An email can be accepted at the server level but still land in the spam folder, so acceptance rate works alongside other metrics like inbox placement rate and spam complaint rate to provide a complete picture of deliverability health.
Why Acceptance Rate Matters
A low acceptance rate signals a sender reputation problem. Recipient servers reject or defer messages from senders they do not trust, and each rejection erodes future deliverability. Monitoring acceptance rate by domain lets you isolate whether the issue is infrastructure-wide or specific to certain mailbox providers like Gmail or Microsoft.
Best Practices
- Investigate any domain where acceptance rate drops below 97%
- Check DNS records, IP reputation and authentication if rejection rates increase
- Distinguish between hard bounces and soft bounces in your calculations
- Monitor acceptance rate by recipient domain rather than in aggregate
Related Glossary Terms
Abandoned Cart Email
An abandoned cart email is an automated message sent to customers who added items to their online shopping cart but left without completing the purchase. It is one of the highest-converting email types in ecommerce.
ARPU (Average Revenue Per User)
ARPU (Average Revenue Per User) is a metric that measures the average revenue generated per email subscriber over a specific period, used to evaluate list value and campaign effectiveness.
Attention Rate
Attention rate is the percentage of email opens that last longer than 5 seconds, distinguishing genuine reads from passive opens, preview-pane views, or Apple MPP auto-loads.
Bounce Classification
Bounce classification uses SMTP codes (550, 551, 552, 553, 554, 450, 451, 452) and enhanced status codes to categorise permanent and transient delivery failures.
Bounce Rate Threshold
A bounce rate threshold is the percentage of hard or soft bounces at which email platforms and ISPs begin to penalise sender reputation, typically around 2-5%.
Bounce Rate
Email bounce rate is the percentage of emails that were rejected by the receiving server before reaching the recipient. It is a key indicator of list health and data quality.