Definition
Submission rate measures the percentage of emails successfully accepted by your sending infrastructure or ESP out of those submitted for delivery. A submission failure means your ESP rejected the email before attempting delivery to the mailbox provider. Common reasons include invalid authentication, formatting errors, attachment size limits, hourly or daily rate limits, and policy violations.
This metric is distinct from delivery rate and bounce rate. A high submission rate (99%+) indicates well-configured sending infrastructure. Low submission rates signal configuration problems that need attention before they affect broader deliverability.
Common Submission Failures
| Failure | Cause | Fix |
|---|---|---|
| Rate limit exceeded | Too many sends in a short period | Implement throttling or increase limits |
| Authentication failure | Missing or incorrect SPF/DKIM | Verify authentication records |
| Invalid recipient format | Malformed email addresses | Validate addresses before submission |
| Attachment too large | Over ESP size limits | Use hosted images and links instead |
| Suspicious content | Triggering ESP policy filters | Review against ESP content policies |
Best Practices
- Monitor submission rate alongside delivery rate for a complete picture
- Investigate any submission failure rate above 1%
- Implement pre-submission validation to catch formatting errors
- Use queuing and throttling to stay within rate limits
- Review changed authentication settings after DNS updates
- Coordinate with your ESP on rate limits during high-volume campaigns
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 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.
Click-to-Open Rate
Click-to-open rate (CTOR) is the percentage of email opens that resulted in at least one click. It measures how compelling your email content is for people who already opened it.
Frequently Asked Questions
A healthy submission rate is 99% or higher. Rates below 99% indicate configuration issues, rate limiting problems, or data quality issues that should be investigated and resolved promptly.
No. Submission rate measures acceptance by your sending infrastructure. Delivery rate measures acceptance by the recipient's mailbox provider after submission. A high submission rate with a low delivery rate indicates deliverability issues (e.g., poor sender reputation) rather than infrastructure problems.