Open rate is the share of delivered emails whose tracking pixel, a tiny image loaded when the message is displayed, was fetched. It was the standard engagement metric until 2021, when Apple Mail Privacy Protection began pre-fetching images for every message whether or not a person opened it, and other clients followed. Reported open rates rose and stopped meaning anything; reply rate and click rate are the honest replacements. In cold email, the tracking pixel itself can lower deliverability, since filters treat image tracking as a bulk-sender signal.
Open rate is still reported by every platform, which is the problem: it is a number that looks like engagement. Use it only for relative comparisons within one audience and one period, never as a target, and switch cold campaigns to plain-text without tracking pixels.
For list quality, open rate once served as a rough proxy for deliverability. Verification before sending replaces that proxy with a direct measurement: the share of addresses that exist.
A nurture campaign reports a 61% open rate and a 0.9% click rate. Half the audience is on Apple Mail, where every message is pre-fetched. The real engaged share is close to the click rate plus replies, around 2%, which is the number the next campaign is judged on.
Verify a list or a single address. 100 free checks a month, unknowns refunded.
Verify Leads - FreeAyoub built BounceZero's 5-stage validation pipeline, its dedicated BGP-announced IP infrastructure, and the Patroni HA PostgreSQL cluster behind every verification. Previously built high-volume email delivery infrastructure. Trained at 1337 Benguerir (École 42 network, 2019). Open-source: bgp_analyzer.