They Sent It

ESPs

An ESP (email service provider) is the tool a brand's team uses to send its marketing email. The 41,419 brands listed here send through 14 ESPs. Klaviyo has the most, with 33,923.

ESPBrandsEmails collectedTypical emails a weekMost common busiest day
Klaviyo33,9231,575,378about 3Tuesday33,923 brands · 1,575,378 emails · about 3 a week
Mailchimp4,209110,644about 2Tuesday4,209 brands · 110,644 emails · about 2 a week
HubSpot2,46274,749about 2Tuesday2,462 brands · 74,749 emails · about 2 a week
ActiveCampaign38816,583about 2Tuesday388 brands · 16,583 emails · about 2 a week
Omnisend1044,539about 4Monday104 brands · 4,539 emails · about 4 a week
Shopify Email741,974about 2Tuesday74 brands · 1,974 emails · about 2 a week
Amazon SES633,443about 5Monday63 brands · 3,443 emails · about 5 a week
Attentive614,460about 3Tuesday61 brands · 4,460 emails · about 3 a week
Kit462,119about 2Thursday46 brands · 2,119 emails · about 2 a week
Drip442,085about 2Wednesday44 brands · 2,085 emails · about 2 a week
Iterable16982about 4Tuesday16 brands · 982 emails · about 4 a week
Emarsys15876about 3Monday15 brands · 876 emails · about 3 a week
Bloomreach13616about 3Monday13 brands · 616 emails · about 3 a week
Cordial1841 brand · 84 emails

Counts cover the brands listed on They Sent It, not every brand that uses each ESP. A brand's ESP is confirmed from its own emails. "Typical" is the middle brand, shown from three brands up. How we collect

Last updated Oct 29, 2026

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