Definition
Custom event tracking in email records specific subscriber actions that go beyond the default metrics of opens and clicks. While every email platform tracks basic engagement, custom events allow marketers to define and measure actions like watching an embedded video, completing a form, scrolling past a certain point, interacting with a poll or saving an offer to a wishlist.
These events are typically implemented through tracking scripts on landing pages, interactive email elements or third-party analytics integrations that communicate with the email platform's API.
Common Custom Events
- Video play, pause and completion
- Poll or survey response submission
- Scroll depth milestones within the email body
- Add-to-calendar or save-for-later actions
- In-email search or filter interactions
- Offer reveal or coupon activation
Best Practices
- Track only events that have a clear link to business outcomes — tracking everything creates noise
- Name events consistently across campaigns so historical analysis is possible
- Use custom events to trigger automated follow-up sequences rather than relying on opens and clicks alone
- Combine custom event data with subscriber profiles to build richer segmentation criteria
Related Glossary Terms
A/B Testing
A/B testing in email marketing is the practice of sending two variations of an email to a small sample of your list to determine which version performs better before sending the winner to the remaining subscribers.
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 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.
Campaign Internal Rate of Return (IRR)
Campaign IRR is the annualised return rate earned by an email campaign, accounting for the timing and magnitude of costs and revenue across the campaign's full lifecycle.
Campaign Lifted Revenue
Campaign lifted revenue is the additional revenue generated by an email campaign beyond what would have occurred without it, measured via a holdout group or statistical lift analysis.