Print email to stdout and log/mail.log

development_email_interceptor.rb

# lib/development_email_interceptor.rb

class DevelopmentMailInterceptor
  def self.delivering_email(message)
    File.open(File.join(Rails.root, *%w{log mail.log}), 'a') do |output|
      output << "___ EMAIL STARTS ______________________________\n"
      output << message.encoded
      output << "^^^ EMAIL ENDS ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n"
    end
    puts "Send email to #{message.to}. Subject: #{message.subject}"
  end
end

email.rb

# config/initializers/email.rb

if Rails.env.development?
  require 'development_mail_interceptor'
  ActionMailer::Base.register_interceptor(DevelopmentMailInterceptor)
end