gistfile1.rb

class NotesController < ApplicationController
  def create
    @note = @project.notes.create params[:note].merge(
      creator: current_user, subscribers: extract_subscribers(params[:note]))
    
    @note.subscribers.each { |subscriber| Subscriptions.note(@note, subscriber).deliver }
  end
end

class Subscriptions < ActionMailer::Base
  def note(note, recipient)
    @note = note
    mail to: recipient.email_address, subject: note.title
  end
end

# To this instead

class NotesController < ApplicationController
  def create
    @note = @project.notes.create params[:note].merge(
      creator: current_user, subscribers: extract_subscribers(params[:note]))
    
    # Returns an a Mailbag of mail objects, that responds to deliver
    Subscriptions.to(@note.subscribers.collect(&:email_address)).note(@note).deliver
  end
end

class Subscriptions < ActionMailer::Base
  def note(note)
    @note = note
    mail subject: note.title
  end
end