Metrics
What is Open Rate?
The percentage of delivered emails that recipients opened, usually measured via a tracking pixel.
Open rate is the number of unique opens divided by delivered emails, traditionally tracked by embedding a tiny invisible image, or pixel, that loads when the message is viewed. The metric has become unreliable since Apple Mail Privacy Protection and image proxies pre-fetch pixels, inflating opens and falsely marking unopened mail as read. Many cold-email operators now treat open rate as a directional signal at best.
Why it matters for cold email
In cold email, open-tracking pixels can themselves hurt deliverability by adding a known tracking domain that spam filters flag, so some senders disable them entirely. Where it is used, open rate is a rough proxy for subject-line and inbox-placement health rather than a precise engagement measure.
Related terms
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