Open Rate

Open rate is the percentage of sent emails that are reported as opened, usually tracked by a 1x1 pixel that loads when the recipient views the message. It is a useful deliverability signal — a sudden drop from 60% to 15% almost always means your domain has been flagged or a segment of your list is landing in spam — but it is a poor performance metric on its own.

Two things make raw open rate unreliable. First, Apple’s Mail Privacy Protection (MPP) silently prefetches images for many recipients, which inflates opens without a human ever having looked at the message. Second, corporate security tools often pre-open email links and images to scan for threats, which also triggers the pixel. You can see 80% open rates on a campaign where nobody actually read a single message.

That does not mean open rate is useless. It is the fastest way to detect a deliverability problem. If open rates collapse mid-sequence, something has changed — the sending domain’s reputation, the copy hitting a new filter, or an inbox provider starting to suppress your mail. Track open rate as a diagnostic tool, not a scoreboard. For real performance, reply rate is honest; open rate is hygiene.

When the term matters

Open rate is the first metric to check when a cold email campaign stops producing meetings. A normal sequence should hold a relatively stable open rate across steps; a sharp drop at step two or three usually means the domain is landing in spam on follow-ups. Pair it with reply rate to see whether you have a deliverability problem or a copy problem.

Related concepts

Open rate is the hygiene metric. Reply rate is the truth metric. Both depend on SPF, DKIM, DMARC, a warmed-up domain, and a clean list.