A SendGrid alternative for transactional email

Moving over

1. 01

   Key and domain

   Create a SpacePost API key and verify your sending domain (three DKIM CNAMEs plus the MAIL FROM records). Keep SendGrid's DNS records until you switch.

2. 02

   Sending calls

   Each personalization becomes one POST /emails call: to, cc, bcc, subject, html or text, reply_to, base64 attachments and custom headers carry over. Use POST /emails/batch for up to 100 messages at once.

3. 03

   Or just SMTP

   Change the host to smtp.spacepost.dev, the port to 25976 with STARTTLS, the username to spacepost and the password to your API key.

4. 04

   Templates

   Render your dynamic templates in your code before sending. Handlebars sources can be reused with any Handlebars library.

5. 05

   Suppressions

   Export bounces, blocks, spam reports and unsubscribes from SendGrid and add each address with POST /suppressions, so you never email them again.

6. 06

   Webhooks

   Create a webhook for the events you use and map SendGrid's event names to ours. Signatures follow Standard Webhooks, so Svix-compatible libraries verify them.

The same message, before and after

// SendGrid v3 Mail Send
await fetch("https://api.sendgrid.com/v3/mail/send", {
  method: "POST",
  headers: { Authorization: `Bearer ${process.env.SENDGRID_API_KEY}`, "Content-Type": "application/json" },
  body: JSON.stringify({
    personalizations: [{ to: [{ email: "ada@example.com" }] }],
    from: { email: "receipts@acme.com", name: "Acme" },
    subject: "Your receipt",
    content: [{ type: "text/html", value: html }],
  }),
});

// SpacePost (Resend-compatible API)
const res = await fetch("https://api.spacepost.dev/emails", {
  method: "POST",
  headers: { Authorization: `Bearer ${process.env.SPACEPOST_API_KEY}`, "Content-Type": "application/json" },
  body: JSON.stringify({
    from: "Acme <receipts@acme.com>",
    to: ["ada@example.com"],
    subject: "Your receipt",
    html,
  }),
});
const { id } = await res.json();