The Email Infrastructure Brief · Jul 2026
ESP share among companies founded in the last 18 months — Q2 2026
Among domains born in the last 18 months that adopted an ESP, Postmark and Resend took a combined 5.1 points of net new share from the incumbents this quarter — measured on the day each switch happened.
We counted esp_switched and esp_adopted Movements across all gTLD domains with a first_seen date inside an 18-month window, mapping SPF include changes to a Provider registry. Each event is dated to the DNS change, not to a survey. n = 214,900 adopting domains.
gTLD zones only; ccTLD signal is certificate-derived and excluded from share math here. Providers that route mail without a distinctive SPF include are under-counted and flagged. Hosted senders (e.g. platform-default sending) are out of scope by design.
Net new share moved to developer-first ESPs
The incumbents still hold the installed base, but among *new* adopters the flow is toward developer-first providers. This is a leading indicator: the switch shows up in DNS months before it shows up in a case study or a churn report.
Switching happens in tight windows
41% of domains that removed one ESP added another within 14 days — the paired remove+add that we classify as a switch. That window is short enough to act on if you see it the week it happens.
Debut cohorts adopt faster than older domains
Domains under 18 months old adopt an ESP a median 22 days sooner after first mail than older domains do, and are more likely to start on a developer-first provider — the earlier you catch them, the more open the stack.
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FirstSeen, “The Email Infrastructure Brief — ESP share among companies founded in the last 18 months, Q2 2026.” firstseen.io/research
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