Email open rate is the percentage of delivered emails that are opened by recipients — calculated as (unique opens ÷ delivered emails) × 100. A 'good' open rate varies significantly by industry and list quality, but general UK benchmarks are 20–35% for B2C and 25–40% for B2B newsletters. Note that since Apple's Mail Privacy Protection (MPP) was introduced in 2021, open rates are artificially inflated for Apple Mail users — platforms pre-load tracking pixels regardless of whether the email is actually opened. This means open rate is now a directional rather than precise metric.
Despite its measurement limitations, open rate remains a useful indicator of list health, subject line effectiveness, and sender reputation. Declining open rates over time signal list fatigue, deteriorating deliverability, or declining subject line quality. Sudden drops in open rate often indicate deliverability problems — emails landing in spam rather than inbox.
What affects email open rate
- Subject line — the single biggest lever; curiosity, specificity, personalisation, and brevity consistently outperform generic subjects
- Preview text — the snippet visible in inbox before opening; treat it as a secondary subject line, not filler
- Sender name — emails sent from 'Anika at Elite Digital' consistently outperform those from 'marketing@company.com'
- Send time — UK data generally favours Tuesday–Thursday mornings or afternoons, but list-specific testing matters more
- List hygiene — inactive contacts drag down open rates; regular list cleaning improves measured performance
- Deliverability — emails in spam generate zero opens; maintaining a good sender reputation keeps emails in the inbox
- Segmentation — relevant emails sent to the right audience open more than generic blasts sent to everyone
The highest-impact actions for improving open rates are: (1) Write better subject lines — test curiosity-driven, question-based, and specific benefit-focused subjects against your current approach. (2) Clean your list — remove contacts who have not opened in 6+ months after a re-engagement attempt. (3) Improve your sending cadence — if you email daily and open rates are declining, reduce frequency. (4) Send from a person's name rather than a company name. (5) Improve inbox placement by authenticating your domain (SPF, DKIM, DMARC) if not already done.
Open rate is still useful as a directional trend metric — if it moves significantly in either direction, something meaningful has changed. However, for campaign-level performance measurement, click-through rate, revenue per send, and conversion rate are more reliable signals since they reflect actual engagement rather than potentially inflated tracking. Many email marketers have shifted their primary optimisation focus to click-to-open rate (CTOR) — which measures clicks relative to opens — as a more meaningful indicator of content relevance, since it is less affected by MPP inflation.