ESPs Are Not Winner-Take-All

The key fact about ESPs is that scale does not collapse the market into one dominant winner, because email customers buy for very different jobs. A Shopify merchant wants revenue attribution and ecommerce flows, a solo writer wants subscriptions and referrals, a startup marketer wants behavioral triggers and CRM data, and an enterprise publisher may run on custom or legacy systems. That keeps the market broad, segmented, and full of durable midsized businesses rather than one universal platform.

• Mailchimp reached about $1B ARR with roughly 35% to 40% share, which implies a category big enough to support many other meaningful vendors. The rest of the market is spread across tools built for distinct user groups, including creators, ecommerce brands, B2B lifecycle marketing teams, and enterprises.
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• Fragmentation is reinforced by product depth. ConvertKit says customers rarely move to Mailchimp, but more technical teams may move to Customer.io or Intercom for heavier API usage and event tracking. In practice, each vendor wins by fitting a workflow, not by becoming the default for everyone.
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• Even inside creator newsletters, there is room for several winners because the products monetize differently. Substack takes a cut of paid subscriptions, ConvertKit sells software and layers on ads and recommendations, and Beehiiv mixes subscription fees with an ad network. The market is segmenting again inside the niche.
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The next phase is more specialization with selective bundling. ESPs will keep adding adjacent revenue tools, like ad sales, recommendations, commerce, and automation, but the winners in each segment will still be the ones that best match a specific user’s workflow, monetization model, and level of technical complexity.