How do you return out of an ActionMailer::Base function?

I'm trying to implement an ActionMailer function that will send out a newsletter to a specific user. I want to make sure that the newsletter is only sent to subscribed users. I tried implementing it like so:

class UserMailer < ActionMailer::Base
  def newsletter(user)
    return unless user.subscribed # This still renders my mailer view

    mail(:to => user.email, :subject => "News开发者_Python百科letter")
  end
end

The problem is that the return unless user.subscribed line still appears to be rendering the mailer view and is still sent by the calling code (from a cron job):

task :cron => :environment do
  User.where(:subscribed => true).each do |user|
    UserMailer.newsletter(user).deliver
  end
end

Note that I do have that subscription logic in my cron job as well for performance reasons (shouldn't have to iterate over ALL users, only those that are subscribed). However, it feels like the UserMailer class is the right place for this logic to exist (otherwise any other location that calls the newsletter method will need to check the subscribed flag as well.

The Mailer, IMHO, is the wrong place for this logic. The mailer should do nothing but format and send messages. The logic to decide whether or not to send should be within the calling block of code. It's not the right way, but something as simple as:

UserMailer.newsletter(user).deliver if user.subscribed?

Alternately, as you mentioned, you shouldn't have to iterate over all users, just the subscribed. So with a scope in the User model called subscribed:

User.subscribed.each do |user|
  UserMailer.newsletter(user).deliver
end

This way you don't need to test on a per-user basis; only the subscribed users are included, and the logic is in the calling block, not in the mailer.