Understanding open rates

Open rates are the most visible email metric — and the most misleading. Here's why, and what to focus on instead.

How open tracking works

Sendra inserts a tiny, transparent 1x1 pixel image in each email. When the recipient's email client loads this image, Sendra records an "open" event.

Since iOS 15, Apple Mail pre-fetches all email content (including tracking pixels) at delivery time, regardless of whether the user actually opens the email. This inflates open rates for any audience with significant Apple Mail usage — which is most consumer audiences.

Image blocking

Some email clients block images by default (especially corporate Outlook installations). These recipients may read your entire email without triggering an open.

Bot pre-fetching

Corporate email gateways and security tools sometimes pre-fetch links and images to scan for threats. These register as opens and clicks even though no human saw the email.

What to measure instead

Click rate

Clicks require deliberate action and are much harder to fake. Click rate (clicks / delivered) is a more reliable engagement signal.

Click-to-open rate

Clicks / opens measures how compelling your content is to people who actually saw it. Useful for A/B testing subject lines vs content.

Unsubscribe rate

Rising unsubscribes signal content fatigue or misaligned expectations. A healthy rate is below 0.5% per campaign.

Reply rate

If your emails generate replies, that's the strongest engagement signal possible. Inbox providers track replies as a positive signal.

Should you disable open tracking?

For most users, no. Open rates are directionally useful even if not perfectly accurate — they help identify trends (declining engagement over time) and compare campaigns against each other.

Disable open tracking if:

Privacy is a core value for your brand
Your audience is privacy-conscious and might be put off by tracking
You need to reduce email size (the tracking pixel adds minimal weight but it's nonzero)