What Is useSend? Open-Source Email for Builders
A practical explanation of useSend, the self-hosted email problem it solves, and how builder-led teams should evaluate it.
Overview
useSend (formerly Unsend) is an open-source, API-first email sending platform for developers who want more control than a fully hosted email API gives them. Its own documentation positions it as an open-source alternative to Resend, SendGrid, Mailgun, and Postmark — a builder-friendly layer for sending email from your own stack. It does not replace a full marketing suite; it's the sending layer, which you own and run.
The appeal is ownership and cost: run it on a server you control, relay delivery through Amazon SES, and pay near-cost for volume instead of a per-contact subscription — attractive when you already use SES, Docker, Coolify, Railway, or a VPS and don't want every email decision living inside a closed platform.
What useSend actually gives you
useSend provides the things you'd expect from a hosted email API, but self-hostable: a REST API and SMTP, a dashboard, domain and API-key management, contact/list support, and email-event tracking. You deploy it (commonly via Docker, Coolify, or Railway), point it at Amazon SES for delivery, and send through a clean API or SMTP — a Resend-style developer experience on infrastructure you own.
The important boundary: useSend is the sending layer, not the mail server. It doesn't run its own MTA or own IP reputation — it relays through SES, so you get a developer-friendly API and dashboard while AWS handles the deliverability-critical IP reputation. That's the right architecture, not a limitation.
- Open-source, self-hostable Resend-style sending API + dashboard
- REST API and SMTP, domain/API-key management, event tracking
- Relays delivery through Amazon SES (you don't run an MTA)
- Deploy via Docker, Coolify, or Railway
Who it's for, and where Mailbase fits
useSend fits developers, indie hackers, and SaaS founders who want to own their sending layer and pay near-cost at volume, and who are comfortable owning deliverability — SPF/DKIM/DMARC, warmup, bounces, suppression — and a bit of ops. It's less suited to a non-technical team that just wants campaigns to work out of the box. Compare it head-to-head in useSend vs Resend.
What useSend doesn't give you is the team workflow above sending: a shared reply inbox, AI drafts, MJML campaigns, A/B tests, scheduled sends, analytics, and a developer API. That's exactly where Mailbase sits — connect your useSend instance (BYO at €5/mo) and you get the workflow layer on delivery you already run, or use Mailbase managed sending if you'd rather not host.
- For: builders who want to own sending and pay near-cost
- You still own deliverability (auth, warmup, bounces, suppression)
- Doesn't include a team workflow (inbox, campaigns, AI)
- Mailbase adds that layer on your useSend (BYO €5/mo) or managed
Common Mistakes
- Choosing a tool before deciding who owns deliverability.
- Treating DNS authentication as a one-time checkbox instead of an operating baseline.
- Mixing product-critical transactional email with experimental marketing sends, with no clear boundary.
- Trusting headline metrics (like open rate) that privacy proxies now inflate.
Sources & Further Reading
Official docs for current setup details, pricing, and API behavior — verify specifics there, since they change.
Related guides
More on what is usesend and the surrounding usesend workflow:
FAQ
What is useSend?
useSend (formerly Unsend) is an open-source, API-first email sending platform you can self-host — a developer-friendly alternative to Resend, SendGrid, Mailgun, and Postmark. It gives you a REST API, SMTP, and a dashboard, and relays delivery through Amazon SES, so you own the sending layer without running a mail server.
Is useSend free?
The software is open-source and free to run; you pay only for hosting and your delivery provider (Amazon SES, at fractions of a cent per email). That makes it near-cost at volume compared to per-contact SaaS pricing — but you take on deliverability and a bit of ops in return.
Do I need AWS SES to use useSend?
Almost always, yes. useSend provides the API, dashboard, and management, but relays through an upstream provider — most commonly Amazon SES — for actual delivery and IP reputation. You self-host the app, not the mail-server reputation.
What's the difference between useSend and Mailbase?
useSend is the sending layer (API, dashboard, domains) you self-host. Mailbase is the workflow layer above sending — shared reply inbox, AI drafts, MJML campaigns, A/B tests, analytics — and it can run on your own useSend instance (BYO at €5/mo) or on managed sending.