Six numbers that matter
Average ROI per $1 spent on email marketing
Source: DMA / Litmus 2025
Active email users worldwide in 2026
Source: Statista
Average open rate in the reviewed Q1 2026 benchmark set
Source: BestSends 2026 research
Spam complaint rate that triggers Gmail throttling
Source: Google Postmaster
Median cost per 1,000 emails sent at the 10K-subscriber tier
Source: BestSends ESP pricing audit
Monthly list decay across audited B2B newsletters
Source: BestSends 2026 ESP review cycle
Four findings from our 2026 review cycle
Apple Mail Privacy Protection has permanently broken open rates as a primary metric
Five years after MPP shipped, the marketers who still optimize against open rate are leaving money on the table. The platforms leading the pack (ActiveCampaign, Klaviyo, Customer.io) all default their dashboards to engagement-weighted metrics now. ESPs still treating "opens" as a first-class metric (Mailchimp, Constant Contact) feel a generation behind.
Free plans got worse — except where they got dramatically better
Mailchimp, Brevo, and AWeber tightened their free plans in 2025–2026. MailerLite, Beehiiv, and Sender expanded theirs. The split is creating two distinct markets: legacy ESPs aggressively pushing paid conversion, and modern challengers using generous free tiers as a long-term acquisition strategy.
Deliverability is the new differentiator
Feature parity is everywhere. What separates leading platforms is what happens after you click send. Deliverability evidence matters alongside authentication support, sender practices, and infrastructure; a dedicated IP or a vendor claim alone does not guarantee inbox placement.
AI features are mostly noise — except for subject lines and copy generation
Every ESP launched “AI” features in 2024–2025. The useful distinction is workflow fit: subject-line ideation and copy drafts can speed up production, while broader AI labels often describe narrow features. Evaluate the output, controls, and data handling rather than the badge.