Question

I’m not only new to Rails, but to development in general, so I apologize if this is a basic question. I have an app where I want to send mass emails (ie newsletter) to users that opt-in. I have two concerns: (1) is my code the most efficient way to process a mass mail (ie do I need to use a for…each statement) and (2) I read other posts on Stack Overflow talking about the importance of the mail server and using delayed jobs to send email.

Other things to note:

• I’m on Heroku
• I was thinking about using SendGrid
• I added delayed job code based on this tutorial

My questions are:

1. Do most people use delayed jobs even for single recipient emails (ie a user registration confirmation)?
2. Is my code the most efficient way to do a mass email?
3. If, for example, there’s 1000 users. Does it make a big difference in resources (ie bandwidth, CPU, etc) if I send everyone the same email with a BCC. If so, do I just pass in a hash to the mailer (ie delete the for…each and change opt_in_user parameter to @opt_in_users) and change the recipient to bcc?

Thanks!

Controller

commmunity_users = UserCommunityRelation.find('community_id = ? and status = ?,'      current_community, "approved" )
@opt_in_users = User.find('opt_in = ?,' true)

@opt_in_users.each do |opt_in_user|
  UserMailer.send_later(:deliver_announcement, opt_in_user)
end    

UserMailer.rb

def announcement(opt_in_user)
  mail(:to => "#{opt_in_user.username} <#{opt_in_user.email}>", :subject => "Huge Announcement!")
end

Answer 1

For bulk sending, you should definitely send it via a service (We use Postbox, SendGrid is another option). In addition to the load on the servers, a service will also probably be better suited to bounces, spam blockers, etc, and it will probably offer extra benefits, such as tracking.

Do most people use delayed jobs even for single recipient emails (ie a user registration confirmation)?

For single user emails, I would go with direct emails in the controller.

Is my code the most efficient way to do a mass email?

You wouldn’t want to have a controller action manage queueing the tasks, as it will affect your sites responsiveness. Use a cron job and rake task to do it in the background.

If, for example, there’s 1000 users. Does it make a big difference in resources (ie bandwidth, CPU, etc) if I send everyone the same email with a BCC. If so, do I just pass in a hash to the mailer (ie delete the for…each and change opt_in_user parameter to @opt_in_users) and change the recipient to bcc?

I think BCC is fine on resource usage, but your server will be getting hit with any bounces, and it is an extra service to manage, hence, I’d go with a service as mentioned earlier

BTW, for the #each vs for…each question, the cost of the iterator is going to be so low that it isn’t worth thinking about IMO.