Ruby

# lib/emails.rb
require 'net/http'
require 'json'
require 'uri'

# The key comes from https://emails.sh/dashboard/api-keys. Keep it in
# ENV['EMAILSSH_API_KEY'], loaded from .env or from Rails credentials.
module Emailssh
  ENDPOINT = URI('https://emails.sh/v1/emails').freeze

  class Refused < StandardError
    attr_reader :code

    def initialize(code, message)
      @code = code
      super("#{code}: #{message}")
    end
  end

  def self.send_email(to:, subject:, html:, from: 'Acme <hello@acme.com>')
    request = Net::HTTP::Post.new(ENDPOINT)
    request['Authorization'] = "Bearer #{ENV.fetch('EMAILSSH_API_KEY')}"
    request['Content-Type'] = 'application/json'
    request.body = JSON.generate(from: from, to: [to], subject: subject, html: html)

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

    body = JSON.parse(response.body)
    unless response.is_a?(Net::HTTPSuccess)
      refusal = body['error']
      raise Refused.new(refusal['code'], "#{refusal['message']} #{refusal['next']}")
    end

    body['id']
  end
end

require_relative 'lib/emails'

begin
  id = Emailssh.send_email(
    to: 'ada@example.com',
    subject: 'Your receipt from Acme',
    html: '<p>Thanks for your order.</p>'
  )
  puts "queued #{id}"
rescue Emailssh::Refused => e
  # e.message carries the sentence saying what to do next.
  warn e.message
end

gem install faraday

require 'faraday'
require 'json'

conn = Faraday.new(url: 'https://emails.sh') do |f|
  f.request :json
  f.response :json
  f.options.timeout = 10
end

response = conn.post('/v1/emails') do |req|
  req.headers['Authorization'] = "Bearer #{ENV.fetch('EMAILSSH_API_KEY')}"
  req.body = {
    from: 'Acme <hello@acme.com>',
    to: ['ada@example.com'],
    subject: 'Your receipt from Acme',
    html: '<p>Thanks for your order.</p>'
  }
end

if response.success?
  puts "queued #{response.body['id']}"
else
  refusal = response.body['error']
  warn "#{refusal['code']}: #{refusal['message']} #{refusal['next']}"
end