Resend
Why Resend
Sends transactional and marketing emails directly from your application with SDKs for multiple languages. It covers batch sending up to 100 messages per request, React-based template building and inbound email handling through MX records. Built for software teams adding email to their product rather than using a separate marketing interface.
What it does
Resend is an email API for developers. You verify a domain, create an API key and send mail from your application with an official SDK, the REST API or plain SMTP. It handles sending, batch sending of up to 100 emails per request, scheduled sends, attachments, inbound email, templates and delivery tracking.
It also has marketing features: contacts, segments, topics, broadcasts you compose in an editor or through the API, and automations that start from custom events. React Email lets you build templates as components in code.
Why you would need it
Every product sends email, and email is easy to get wrong. A sign-up confirmation that lands in spam means a lost user. A receipt that never arrives means a support ticket. Sending from your own server or a personal mailbox rarely works at any volume.
You feel it the first time password resets go missing. A sending service gives you domain authentication, bounce handling and logs, so you can see what happened to each message.
Where it fits
Resend sits under your product as the sending layer. Your app calls the API when something happens, and Resend delivers the message and reports what happened through webhooks. It works with the usual hosting and back-end stacks, and its docs include guides for Vercel, Supabase, Auth0 and WordPress through SMTP.
It replaces a self-run mail server or an older email API. For marketing it can sit beside a campaign tool, though it also has broadcasts of its own.
What stands out
- Official SDKs for Node.js, Python, PHP, Ruby, Go, Java, Rust, Elixir and .NET, plus SMTP and a CLI.
- Inbound email with webhooks, so your app can react to replies.
- Webhooks with signature verification, retries and replays.
- A hosted MCP server and an AI onboarding guide in the docs.
My take
Resend is a good default for a developer-led team. The setup is quick, the docs are clear and it covers both transactional and marketing mail. There is a free plan, so you can send real mail before you pay.
What I would watch is that it is a developer tool. A marketer who wants to build a campaign visually will still need an engineer for the setup, and the marketing side is simpler than a full email platform. Deliverability also remains your job: you still need a clean domain, DMARC and sensible sending habits.
Verdict
Pick Resend if you build a product and want reliable transactional email with a modern API. Skip it if you need a visual campaign and automation suite for a marketing team. Brevo or Customer.io fit that better.
Notes
Your note
Before you choose
The free plan has daily and domain limits
The free plan has an email allowance each month, a daily limit, a small number of domains and one webhook endpoint. That is enough to build and test. A live product will soon need Pro or Scale, which lift the daily limit and add domains. Check which limits matter for you.
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Marketing and transactional are priced separately
Transactional and marketing email have their own plans, and marketing is based on contacts. If you plan to send both, price them together. Add-ons such as extra domains, a dedicated IP and single sign-on cost extra.
Deliverability depends on you
Resend gives you DMARC and BIMI guides, bounce and suppression handling and deliverability insights. It does not remove the need for a good domain setup and clean lists. Plan time to configure it before launch.
Compare it with the alternatives
Customer.io, Brevo and Loops cover more of the marketing side. For pure sending, compare options on SDK quality, pricing at your volume and how long it takes to get a first email out.