Blocks MailCraft: The Email Editor You Own
Most email editors rent you a subscription and keep your templates in their format. Blocks MailCraft is MIT-licensed, free, and speaks plain HTML both ways. Your brand, your storage, your exit. Try it: mailcraft.seliseblocks.com
A look at what happens when an enterprise software company open-sources its drag-and-drop email editor: no license fee, no subscription, and templates that remain yours in plain HTML. For marketing and product leaders weighing email tooling, the interesting parts are the cost line, the control, and the exit.
The bill that comes with rented email tooling
Most teams build campaigns in a hosted editor that rents by the month and per seat. The designs live in the vendor's private format. The day you want to leave, you export what the exporter gives you and rebuild the rest. Along the way, the brand controls you wanted, from removing the vendor's logo to matching your own fonts, sat behind an enterprise tier. Your product images sat on the vendor's servers, because the editor had no other place to put them.
None of that is a scandal. It is a business model, and the industry accepted it because the alternative meant commissioning an editor from an engineering team, at a cost that kept the idea off the roadmap.
SELISE Digital Platforms changed the terms of that trade. Its drag-and-drop email editor, Blocks MailCraft, ships as a free, MIT-licensed component. The license permits use, modification, embedding in commercial products, and resale, with the copyright notice kept. No subscription tiers exist to upgrade into. The editor carries no fee at all; your sending costs stay whatever they already are with the provider you already use.
Templates that remain yours
Every template in MailCraft is a plain HTML file. The editor accepts an HTML email and returns send-ready HTML, and the file it returns is the file it accepts back. A campaign built this year opens next year, in this editor or any other tool that reads email HTML, which is all of them.
The exit clause matters even for teams that never use it. Vendor lock-in prices itself into every renewal negotiation. When your templates are files on your own disk, in the industry's most portable format, the negotiation changes shape: you stay because the tool earns it, not because leaving costs a quarter of rework.
The engineering behind that promise is visible and testable. The project maintains a test suite dedicated to round-trip fidelity, with one assertion per inspector control, and its changelog records export, import, and export again converging to identical bytes from the first save. In plainer terms: what you save is what you load back, and the team tests that promise continuously rather than asserting it in a sales deck.
Your brand, your systems, your costs
The controls that hosted tools reserve for enterprise pricing sit in the open here, documented in the README:
White-labeling. The editor's SELISE footer comes off with one attribute,
footer="none", and the toolbar can be reduced or removed.Brand match. Accent color, fonts, and light and dark themes follow your product, not the editor's defaults.
Your storage. Image uploads go to a backend you choose. With none configured, uploads stay local to the draft and the editor moves no files anywhere. The README commits to this in a single line: the editor never talks to a backend of its own. For regulated teams, campaign assets never transit a third party's servers.
Your AI budget. The built-in AI drafting panel connects to a provider you supply. The model, the keys, and the invoice stay with you, and the panel is optional.
International reach. Thirty-one languages with automatic right-to-left support, which covers markets that per-locale add-ons usually monetize.
Merge tags and conditional content export in the standard {{first_name}}, {{#if}} notation, so the editor drops into the sending service you already run. That is the whole integration story, and it is why the price can be zero: MailCraft replaces neither your sender nor your data, so there is nothing upstream to bill you for.
A product inside your product
For companies whose software sends email on behalf of customers, an email builder is a feature request that arrives with a build-versus-buy problem attached. Building one in-house means owning table-based Outlook rendering, importer sanitization, undo history, and localization. The depth of that work is measurable in this repo alone: fifteen test suites and a changelog dense with fidelity fixes across dozens of styling controls. That changelog is a fair map of what a from-scratch build signs up for.
MailCraft compresses the decision. One install command, and a working editor mounts in the product.
npm install @seliseblocks/mailcraftNo runtime dependencies ride along, no vendor backend receives customer data, and the MIT license covers commercial embedding and resale. The editor speaks HTML in both directions, so templates created inside a customer's account remain portable files, a retention argument you can make honestly.
Why a software company gives this away
SELISE builds Blocks, an enterprise platform sold to banks, insurers, and healthcare companies. Open-sourcing the email editor is not a weekend gesture. The wider Blocks catalog, from identity and workflow to the CLI and monitoring, is MIT-licensed in public repositories. Twelve of those repos carry the license today, and the count is verifiable in minutes by anyone evaluating the platform.
The commercial logic is legible: the platform competes on services and infrastructure, not on widget licensing, and every team that adopts the free editor gains a reason to look at the paid platform behind it. Buyers get the upside regardless of motive. A component with no fee, an auditable codebase, and a public issue tracker is a better procurement conversation than a closed SDK behind a sales call.
The maintenance record is public too. The project released its first version on August 30, 2026 and shipped eighteen further releases in the following week, each documented in a changelog that follows the industry-standard Keep a Changelog format. That log records the team removing its own Embed block because Gmail and Outlook strip the underlying technology from delivered mail. A vendor that documents the reasoning behind cutting its own feature, in public, is telling you how it will behave when something breaks.
Evaluate it before the first meeting
The demo opens in a browser at mailcraft.seliseblocks.com, with no account and no sales contact, and the documentation and full source sit beside it. Five minutes tells you whether the editor matches your team's expectations; an afternoon inside the repository tells you whether the engineering holds up.
For teams that want the next step, the install is one command, the demo doubles as a template library with eighteen ready campaign files, and contributions follow a public guide. The editor is free in both senses. What it costs to find out is a browser tab.
Try it: mailcraft.seliseblocks.com
