Send email asynchroniously using Sidekiq.

Create your mailer us usual:

# app/mailers/users_mailer.rb

class UsersMailer < ActionMailer::Base

def welcome_email(user_id)
    @user = User.find(user_id)

    mail(   :to      => @user.email,
            :subject => "Welcome"
    ) do |format|
      format.text
      format.html
    end
  end
end

Send email:

user = User.find(1)

mail = UsersMailer.welcome_email(user.id)
#mail.deliver_now
mail.deliver_later

    

Gemfile:

gem 'sidekiq'

bundle exec sidekiq --environment development -C config/sidekiq.yml 

Use god for monitoring and running sidekiq automatically: https://gist.github.com/maxivak/05847dc7f558d5ef282e