day3

day3 is an email service that combines marketing campaigns and transactional messages under one monthly send allowance. Its main difference is what it meters. Paid plans charge for the number of emails sent rather than the number of subscribers stored, so a growing audience doesn't increase the bill during a quiet month. A startup can keep its product updates, changelogs, password resets, and receipts in one service, on one verified domain, without buying separate campaign and developer email products. The product is deliberately narrower than a broad marketing platform and is aimed at teams that want to write, send, automate, and track permission-based email without adding a CRM or sales funnel system.

Setup covers domains, senders, audiences, signup forms, and campaign drafts. If a domain uses Cloudflare, day3 can connect to the account and write the DKIM, SPF, and DMARC records, then keep checking until verification completes. Campaign delivery runs in batches behind a hard monthly cap, so a retry doesn't duplicate messages and a rate limit can pause a send until it is safe to resume. After delivery, activity is searchable per campaign and per person, including delivered, opened, clicked, bounced, unsubscribed, and complaint events. Bad addresses and opt-outs are suppressed automatically, and every message includes a visible unsubscribe route with standards-based one-click handling.

The campaign side includes a focused composer for updates and launch notes, audience imports, and forms that can be published as hosted pages, embeds, popups, or raw HTML. Automations let a user draw a trigger, an email, a wait, and a branch on a canvas, then publish the flow for new contacts to enter. Welcome series and onboarding sequences can run without manual sends, with unlimited flows listed on every plan. Automations are real and can send live email, but day3 labels them as an early preview feature. An AI assistant for drafts, subject lines, and selected-text rewrites is included on paid plans, while engagement and deliverability data stays visible at both campaign and contact level.

Developers get a JSON REST API for transactional email, contacts, audiences, and campaigns. Requests use bearer keys, and an idempotency key keeps a retried transactional call from sending twice. Contact upserts can address a person by email or identifier, while previously unknown attributes become merge tags that campaigns can use. The migration path explicitly asks teams to import old suppressions and unsubscribed contacts before adding active audience members, reducing the risk of mailing someone who already opted out. An MCP endpoint can also let Claude Code, Cursor, or VS Code draft campaigns from the editor. Ordinary keys can draft and test, while reaching a real audience requires a key created with that permission. MCP drafts arrive as editable blocks instead of raw HTML and can be read back as Markdown. The endpoint uses the same bearer key as REST, so access can be revoked in one place.

day3 fits startups, indie developers, SaaS teams, and EU companies that add subscribers quickly but send occasionally. It is especially sensible when list size and send volume have drifted far apart, since paid tiers include unlimited subscribers and change only with the monthly message allowance. It is less suited to agencies managing many client accounts or marketing teams that need A/B tests, landing pages, a CRM, and complex funnels. The service accepts permission-based product communication, not cold outreach or purchased lists. It is built by a small Danish company, runs in the European Union, publishes its subprocessors and data processing agreement, and uses Amazon SES in an EU region for delivery.

The free sandbox supports domain setup, audience import, drafts, the transactional API, tracking, and up to 100 real emails each month to members of the user's own organization. The sandbox allows up to 500 subscribers, while paid plans remove the subscriber limit and unlock sending to the wider audience. Paid pricing begins at $1 per month for 1,000 emails, with published self-serve tiers rising to $220 for one million. A 10,000 email allowance costs $5 per month. Unused sends don't roll over, and sending pauses at the plan cap instead of creating an overage bill. Teams can change tiers as their rhythm changes, and dropping to free retains their audiences, domains, drafts, and history. That makes the free plan useful for a complete test and the paid commitment unusually small for a live send.