Definition
Acceptance rate measures the percentage of emails that are accepted by the recipient's mail server after passing initial filtering. A high acceptance rate means your emails are reaching their intended destination — the mailbox provider. A low acceptance rate means your emails are being rejected at the server level before delivery filtering even begins.
Acceptance rate is distinct from delivery rate (accepted + delivered to inbox) and inbox placement rate (delivered to primary inbox). It represents the first gate: if your email is not accepted, it cannot be delivered. Acceptance failures are typically caused by invalid recipient domains, blacklisted sending IPs, or authentication failures.
Acceptance Rate vs Related Metrics
| Metric | What It Measures | Healthy Rate |
|---|---|---|
| Submission rate | Accepted by your ESP | 99%+ |
| Acceptance rate | Accepted by recipient server | 97%+ |
| Delivery rate | Actually delivered (not bounced) | 97%+ |
| Inbox placement rate | Landed in inbox (not spam) | 90%+ |
Best Practices
- Monitor acceptance rate alongside bounce rate for complete delivery insight
- Investigate acceptance rates below 97% for sending infrastructure issues
- Check blacklist status if acceptance drops suddenly
- Verify authentication records (SPF, DKIM, DMARC) are configured correctly
- Ensure MX records for recipient domains are valid
- Use a deliverability monitoring tool to track acceptance rate trends
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.
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
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.
Click-Through Rate
Click-through rate (CTR) is the percentage of email recipients who clicked one or more links in your email campaign. It measures how compelling your content and call-to-action are.
Click-to-Convert Rate
Click-to-convert rate measures the percentage of email clicks that result in a desired conversion action such as a purchase, signup, or download. It shows how effective your post-click experience is at turning interest into results.
Frequently Asked Questions
Common causes include blacklisted sending IP or domain, incorrect or missing authentication records, sending to invalid or expired domains, rate limiting or throttling by mailbox providers, and technical issues with your sending infrastructure (MTA configuration, DNS problems).
Check your IP and domain against major blacklists and delist if necessary. Verify that SPF, DKIM, and DMARC are correctly configured. Remove invalid addresses from your list. Stagger your sending volume if you are being rate-limited. Ensure your MTA and DNS infrastructure is correctly configured and maintained.