Redmine/config/initializers/10-patches.rb

ActiveRecord::Errors.default_error_messages = {
  :inclusion => "activerecord_error_inclusion",
  :exclusion => "activerecord_error_exclusion",
  :invalid => "activerecord_error_invalid",
  :confirmation => "activerecord_error_confirmation",
  :accepted  => "activerecord_error_accepted",
  :empty => "activerecord_error_empty",
  :blank => "activerecord_error_blank",
  :too_long => "activerecord_error_too_long",
  :too_short => "activerecord_error_too_short",
  :wrong_length => "activerecord_error_wrong_length",
  :taken => "activerecord_error_taken",
  :not_a_number => "activerecord_error_not_a_number"
} if ActiveRecord::Errors.respond_to?('default_error_messages=')

ActionView::Base.field_error_proc = Proc.new{ |html_tag, instance| "#{html_tag}" }

# Adds :async_smtp and :async_sendmail delivery methods
# to perform email deliveries asynchronously
module AsynchronousMailer
  %w(smtp sendmail).each do |type|
    define_method("perform_delivery_async_#{type}") do |mail|
      Thread.start do
        send "perform_delivery_#{type}", mail
      end      
    end
  end
end

ActionMailer::Base.send :include, AsynchronousMailer