Send email with Ruby

Net::HTTP and nothing else: one POST, explicit status checks, done.

Facts verified 2026-07-17 — corrections: hello@emailfast.dev

Ruby's Net::HTTP handles the Email Fast API without a single gem: one JSON POST, one bearer header, one status check. If you'd rather have a typed client, the Ruby SDK quickstart covers it; on Rails, the Rails guide wraps this call in a service object and a job.

# send.rb — Ruby 3.x, stdlib only
require "json"
require "net/http"
require "uri"

uri = URI("https://api.emailfast.dev/v1/emails")

req = Net::HTTP::Post.new(uri)
req["Authorization"] = "Bearer #{ENV.fetch("EMAILFAST_API_KEY")}" # ef_sandbox_... while testing
req["Content-Type"] = "application/json"
req.body = JSON.generate(
  to: "ada@example.com",
  subject: "Welcome",
  html: "<h1>Hi {{name}}</h1>",
  data: { name: "Ada" },
  idempotency_key: "welcome-ada-1" # a retry replays, never re-sends
)

res = Net::HTTP.start(uri.host, uri.port, use_ssl: true, read_timeout: 10) do |http|
  http.request(req)
end

raise "Send rejected (#{res.code}): #{res.body}" unless res.is_a?(Net::HTTPSuccess)

result = JSON.parse(res.body)
puts "#{result["id"]} #{result["status"]}" # msg_... queued

a 202 from the API means the send is committed to a durable, partitioned outbox before we answer — a crash can't lose it, and a retry with the same idempotency key can't double-send.

Gotchas

• Net::HTTP does not raise on 4xx/5xx — it hands you the error response and moves on. Check Net::HTTPSuccess yourself; the JSON body names the exact rejection.
• use_ssl: true is not inferred from the URL. Forget it and the request talks plaintext to port 443 and fails confusingly.
• ENV.fetch (not ENV[]) fails loudly at boot when the key is missing — the failure you want.
• Sending many? Keep the Net::HTTP.start block open and reuse the connection, or POST up to 500 messages to /v1/emails/batch in one call.

Next

• Ruby SDK quickstart — the typed client
• The email API — batch, scheduling, message timelines
• Sending from Rails
• All docs