Choosing your emailing tool (ESP): the engine of the stack

A decision you make for two years, not for one evening

The ESP — Email Service Provider, the tool that sends, segments and automates — is the engine of your stack. It's also a costly choice to change: migrating a list, its automations, its forms and its history takes time and loses data. So choose based on where you're going, not just on the entry price. Three questions settle it: what do I sell (content, physical product, e-commerce, service)? what list size and what ambition? how much technical time can I devote to it?

An ESP isn't chosen on the first month's price, but on what it will let you do once your list has multiplied by ten.

The main families of tools

The market sorts into families, depending on the slider between simplicity, automation and budget:

• Accessible general-purpose ESPs — Brevo (formerly Sendinblue, free up to 300 sends/day, then by volume), MailerLite (free up to 1,000 subscribers), Mailchimp (the best known, quickly expensive as you scale): perfect to start, send campaigns and simple automations.
• Creator & content-oriented ESPs — Kit (formerly ConvertKit), MailerLite: built for creators, bloggers, coaches; excellent for sequences, tags and selling digital products.
• Advanced e-commerce ESPs — Klaviyo, Omnisend: deep integration with Shopify/WooCommerce, behavioral segmentation, abandoned-cart scenarios; powerful but pricier.
• Newsletter platforms — Substack (free, takes 10% of paid subscriptions), Beehiiv, Ghost: built to publish a newsletter and monetize it, with less marketing automation but a real editing experience (covered in chapter 8).

Matching the tool to the project

What really matters in the choice

Beyond the brand name, a few criteria decide in practice. Segmentation and tags: being able to send the right message to a subgroup (customers vs. prospects, interested in a topic) changes the whole return. Automation: the quality of the scenario editor determines what you'll be able to run on your own. Integrations: your ESP must connect to your site, your store, your forms, or via Zapier / Make. Deliverability and the platform's reputation. And the pricing model: billing by number of subscribers (you pay even for inactives) or by send volume?

The trap of price exploding as you scale

Many tools are free or cheap at 500 contacts, then become steep at 5,000 or 20,000. Mailchimp is the classic example: pleasant at the start, quickly costly. Before getting attached to a tool, look at the tier you'll be at a year from now, not just the entry plan. Tip: tools that bill by number of subscribers reward a clean list (cleaning out inactives lowers the bill); those that bill by send volume suit large, rarely solicited lists. Choosing the right pricing model means avoiding a nasty surprise at 10,000 subscribers.

Migrating later without pain

Changing ESP isn't dramatic if you anticipate it. What migrates easily: contacts (CSV export/import) and email content. What's lost or rebuilt: automations (to recreate by hand), forms (new codes to embed), and part of the engagement history. Practical consequence: don't over-invest in complex automations on a tool you sense is temporary, and always keep a recent export of your list — it's your asset, it must stay under your control, never held hostage by a platform.

Key takeaways

The ESP is the engine of the stack: choose it on your trajectory, not on the first month's price. MailerLite and Brevo are excellent free starting points; Kit shines for creators; Klaviyo and Omnisend for e-commerce; Substack, Beehiiv and Ghost to publish a newsletter. Look at segmentation, automation, integrations, deliverability and especially the pricing model at the tier you'll be at a year from now. Always keep an export of your list at hand: it belongs to you. With the tool chosen, you still have to make it say something worth opening: let's write emails that convert.