ActionMailer SMTP config is a nightmare

# app/services/email_service.rb
class EmailService
  def initialize
    @ark = Ark::Client.new(api_key: Rails.application.credentials.ark_api_key)
  end

  def welcome(user)
    # Returns response with ID, raises on error
    @ark.emails.send(
      from: "[email protected]",
      to: user.email,
      subject: "Welcome, #{user.name}!",
      html: render_template("welcome", user: user)
    )
  end

  private

  def render_template(name, locals = {})
    ApplicationController.render(
      template: "emails/#{name}",
      layout: "email",
      locals: locals
    )
  end
end

# Usage: EmailService.new.welcome(user)

# app/jobs/send_email_job.rb
class SendEmailJob
  include Sidekiq::Job

  # Ark is fast—each job completes in ~100ms instead of 2-5s with SMTP
  def perform(to:, subject:, html:)
    ark = Ark::Client.new(api_key: Rails.application.credentials.ark_api_key)

    ark.emails.send(
      from: "[email protected]",
      to: to,
      subject: subject,
      html: html
    )
  end
end

# Bulk send 10,000 emails:
# With ActionMailer SMTP: 40+ minutes (SMTP handshake per email)
# With Ark HTTP: ~2 minutes (parallel HTTP requests)
users.each do |user|
  SendEmailJob.perform_async(
    to: user.email,
    subject: "Weekly digest",
    html: render_digest(user)
  )
end

# app.rb
require "sinatra"
require "ark"

# Works anywhere—not tied to Rails conventions
ark = Ark::Client.new(api_key: ENV["ARK_API_KEY"])

post "/contact" do
  content_type :json

  data = JSON.parse(request.body.read)

  begin
    ark.emails.send(
      from: "[email protected]",
      to: "[email protected]",
      reply_to: data["email"],
      subject: "Contact form: #{data["subject"]}",
      text: data["message"]
    )
    { success: true }.to_json
  rescue Ark::Error => e
    # Clear error—you know exactly what failed
    status 500
    { error: e.message }.to_json
  end
end