Open Rate
Open rate is the percentage of delivered emails that were opened by recipients, calculated as (unique opens ÷ delivered emails) × 100.
What Is Open Rate?
Open rate is traditionally measured using a tiny invisible tracking pixel embedded in the email. When a recipient loads images in the email, the pixel fires and registers an open. However, open rate has become less reliable as a metric since Apple introduced Mail Privacy Protection (MPP) in iOS 15. MPP pre-fetches tracking pixels regardless of whether the user actually reads the email, artificially inflating open rates. Despite these limitations, open rate remains a useful directional metric when tracked consistently over time. Average newsletter open rates typically range from 20-40%, depending on the niche and list quality.
Why It Matters for Newsletters
Open rate is the first indicator of whether your subject lines and send times are effective. A declining open rate can signal problems with subject line quality, send frequency, list fatigue, or deliverability issues. While it shouldn't be your only metric, it's a valuable early warning signal.
Best Practices
- Focus on trends rather than absolute numbers — Apple MPP has inflated raw open rates
- A/B test subject lines to find what resonates with your audience
- Optimise send times based on when your subscribers are most active
- Segment your list and track open rates per segment for more meaningful data
- Use open rate alongside click rate for a fuller picture of engagement
How Aldus Handles This
Aldus automatically A/B tests subject lines on every send, optimising for open rates over time. The platform's AI also learns which types of subject lines perform best for your specific audience and adjusts its approach accordingly.