Automatically Unsubscribe from Emails in Rails (and Control Email Preferences)

In this tutorial, I’ll show you how to add a link to any Rails Mailer that will allow a user to automatically unsubscribe from that email. As an added bonus, we’ll build a page allowing a user to update their email preferences across all mailers.

Inspired by GoRails.

demoClick to expand

Step 1: Build Mailers

  1. Generate mailers.

    rails g mailer marketing promotion
    rails g mailer notification notify
    
  2. Update previews by passing a user into the mailer. This assumes your database has at least one user record.

    # test/mailers/previews/marketing_mailer_preview.rb
    
    class MarketingMailerPreview < ActionMailer::Preview
      def promotion
        MarketingMailer.with(user: User.first).promotion
      end
    end
    
    # test/mailers/previews/notification_mailer_preview.rb
    
    class NotificationMailerPreview < ActionMailer::Preview
      def notify
        NotificationMailer.with(user: User.first).notify
      end
    end
    

Step 2: Build a Model to Save Email Preferences

  1. Generate the model and migration.

    rails g model mailer_subscription user:references subscribed:boolean mailer:string
    
  2. Add a null constraint to the mailer column, and a unique index on the user_id and mailer columns. This will prevent duplicate records.

    class CreateMailerSubscriptions < ActiveRecord::Migration[6.1]
      def change
        create_table :mailer_subscriptions do |t|
          t.references :user, null: false, foreign_key: true
          t.boolean :subscribed
          t.string :mailer, null: false
    
          t.timestamps
        end
    
        add_index(:mailer_subscriptions, [:user_id, :mailer], unique: true)
      end
    end
    

    What’s Going On Here?

    • We add null: false to the mailer column to prevent empty values from being saved, since this column is required.
    • We add a unique index on the user_id and mailer columns to prevent a user from having multiple preferences for a mailer.
  3. Run the migrations.

    rails db:migrate
    
  4. Build the MailerSubscription model.

    # app/models/mailer_subscription.rb
    
    class MailerSubscription < ApplicationRecord
      belongs_to :user
    
      MAILERS =
        OpenStruct.new(
          items: [
            {
              class: "MarketingMailer",
              name: "Marketing Emails",
              description: "Updates on promotions and sales.",
            },
            {
              class: "NotificationMailer",
              name: "Notification Emails",
              description: "Notifications from the website.",
            },
          ],
        ).freeze
    
      validates :subscribed, inclusion: [true, false], allow_nil: true
      validates :mailer, presence: true
      validates :mailer, inclusion: MAILERS.items.map { |item| item[:class] }
      validates :user, uniqueness: { scope: :mailer }
    
      # @mailer_subscription.details
      # => [{:class => "MarketingMailer", :name => "Marketing Emails", :description => "Updates on promotions and sales."}]
      def details
        MailerSubscription::MAILERS.items.select { |item| item[:class] == mailer }
      end
    
      # @mailer_subscription.name
      # => "Marketing Emails"
      def name
        details[0][:name]
      end
    
      # @mailer_subscription.name
      # => "Updates on promotions and sales."
      def description
        details[0][:description]
      end
    
      # @mailer_subscription.name
      # => "Subscribe to"
      def action
        subscribed? ? "Unsubscribe from" : "Subscribe to"
      end
    
      # @mailer_subscription.name
      # => "Subscribe to Marketing Emails"
      def call_to_action
        "#{action} #{name}"
      end
    end
    

    What’s Going On Here

    • We add a constant to store a list of mailers a user will be able to subscribe/unsubscribe from. The class value must match the name of a Mailer class.
    • We use the values stored in the constant to constrain what values can be set on the mailer column. This prevents us from accidentally creating a record with an invalid mailer.
    • We add a uniqueness validator between the user and mailer. This is made possible by the unique index we created in the migration. This will ensure a user cannot have multiple preferences for the same mailer.
    • We use the values stored in the constant to create a variety of helper methods that can be used in views.
  5. Add method to check if a user is subscribed to a specific mailer.

    # app/models/user.rb
    
    class User < ApplicationRecord
      has_many :mailer_subscriptions, dependent: :destroy
    
      # @user.subscribed_to_mailer? "MarketingMailer"
      # => true
      def subscribed_to_mailer?(mailer)
        MailerSubscription.find_by(
          user: self,
          mailer: mailer,
          subscribed: true,
        ).present?
      end
    end
    

What’s Going On Here?

  • We add a method that checks if a user is subscribed to a particular mailer. If the method finds a matching record, then the user is subscribed. Otherwise, they are not. Note that this is an opt-in strategy. We’re deliberately looking for records where subscribed is set to true. This means that if there is no record in the database, they’ll be considered unsubscribed.
  • To make this an opt-out strategy, you could simply replace subscribed: true with subscribed: false.

Step 3: Allow a User to Automatically Unsubscribe from a Mailer

  1. Generate a controller to handle automatic unsubscribes.

    rails g controller mailer_subscription_unsubcribes
    
    # config/routes.rb
    
    Rails.application.routes.draw do
      ...
      resources :mailer_subscription_unsubcribes, only: %i[show update]
    end
    
  2. Build the endpoints.

    # app/controllers/mailer_subscription_unsubcribes_controller.rb
    
    class MailerSubscriptionUnsubcribesController < ApplicationController
      before_action :set_user, only: %i[show update]
      before_action :set_mailer_subscription, only: %i[show update]
    
      def show
        if @mailer_subscription.update(subscribed: false)
          @message = "You've successfully unsubscribed from this email."
        else
          @message = "There was an error"
        end
      end
    
      def update
        if @mailer_subscription.toggle!(:subscribed)
          redirect_to root_path, notice: "Subscription updated."
        else
          redirect_to root_path, notice: "There was an error."
        end
      end
    
      private
    
      def set_user
        @user = GlobalID::Locator.locate_signed params[:id]
        @message = "There was an error" if @user.nil?
      end
    
      def set_mailer_subscription
        @mailer_subscription =
          MailerSubscription.find_or_initialize_by(
            user: @user,
            mailer: params[:mailer],
          )
      end
    end
    
  3. Build the view.

    <%# app/views/mailer_subscription_unsubcribes/show.html.erb %>
    <h1>Unsubscribe</h1>
    <p><%= @message %></p>
    
    <%= button_to @mailer_subscription.call_to_action, mailer_subscription_unsubcribe_path, method: :patch, params: { mailer: params[:mailer] } if @mailer_subscription.present? %>
    

You can test this be getting the Global ID of a user and going to the endpoint.

User.first.to_sgid.to_s

# => "abc123..."

http://localhost:3000/mailer_subscription_unsubcribes/abc123…?mailer=MarketingMailer

Page where a user can auto unsubscribe from mailerClick to expand

What’s Going On Here?

  • We create an endpoint that will automatically unsubscribe a user from a particular mailer. This is a little unconventional since we’re creating a record on a GET request (instead of a POST request). We’re forced to do this because a user will be clicking a link from an email to unsubscribe. If emails supported forms, we could create a POST request.
  • We add a button on that page that will allow the user to resubscribe to the mailer. Note that we don’t redirect back to the show action because that would end up unsubscribing the user from the mailer again.
  • We find the user through their GlobalID in the URL which makes the URLs difficult to discover. Otherwise the URL would just accept the user’s ID which is much easier to guess. This will prevent a bad actor from from unsubscribing a user from a mailer.

Step 4: Build a Page for User to Update Their Email Preferences

  1. Generate a controller for the MailerSubscription model.

    rails g controller mailer_subscriptions
    
    # config/routes.rb
    
    Rails.application.routes.draw do
      resources :mailer_subscription_unsubcribes, only: %i[show update]
      resources :mailer_subscriptions, only: %i[index create update]
    end
    
  2. Build the endpoints.

    # app/controllers/mailer_subscriptions_controller.rb
    class MailerSubscriptionsController < ApplicationController
      before_action :authenticate_user!
      before_action :set_mailer_subscription, only: :update
      before_action :handle_unauthorized, only: :update
    
      def index
        @mailer_subscriptions = MailerSubscription::MAILERS.items.map do |item|
          MailerSubscription.find_or_initialize_by(mailer: item[:class], user: current_user)
        end
      end
    
      def create
        @mailer_subscription = current_user.mailer_subscriptions.build(mailer_subscription_params)
        @mailer_subscription.subscribed = true
        if @mailer_subscription.save
          redirect_to mailer_subscriptions_path, notice: "Preferences updated."
        else
          redirect_to mailer_subscriptions_path, alter: "#{@mailer_subscription.errors.full_messages.to_sentence}"
        end
      end
    
      def update
        if @mailer_subscription.toggle!(:subscribed)
          redirect_to mailer_subscriptions_path, notice: "Preferences updated."
        else
          redirect_to mailer_subscriptions_path, alter: "#{@mailer_subscription.errors.full_messages.to_sentence}"
        end
      end
    
      private
    
        def mailer_subscription_params
          params.require(:mailer_subscription).permit(:mailer)
        end
    
        def set_mailer_subscription
          @mailer_subscription = MailerSubscription.find(params[:id])
        end
    
        def handle_unauthorized
          redirect_to root_path, status: :unauthorized, notice: "Unauthorized." and return if current_user != @mailer_subscription.user
        end
    end
    

    What’s Going On Here?

    • We create a page allowing a user to subscribe/unsubscribe from all possible mailers that are defined in MailerSubscription::MAILERS. We can’t call @user.mailer_subscriptions because they may not have any records.
    • We create a handle_unauthorized method to prevent a user from subscribing/unsubscribing another user from mailers. We need to do this because we’re passing in the ID of the MailerSubscription through the params hash which can be altered via the browser.
  3. Build the views.

    <%# app/views/mailer_subscriptions/index.html.erb %>
    
    <ul style="list-style:none;">
      <%= render @mailer_subscriptions %>
    </ul>
    
    <%# app/views/mailer_subscriptions/_mailer_subscription.html.erb %>
    <% if mailer_subscription.new_record? %>
    
      <li style="margin-bottom: 16px;">
        <p><%= mailer_subscription.description %></p>
        <%= button_to mailer_subscriptions_path, params: { mailer_subscription:  mailer_subscription.attributes } do %>
          <%= mailer_subscription.call_to_action %>
        <% end %>
        <hr/>
      </li>
    <% else %>
      <li style="margin-bottom: 16px;">
        <p><%= mailer_subscription.description %></p>
        <%= button_to mailer_subscription_path(mailer_subscription), method: :put do %>
          <%= mailer_subscription.call_to_action %>
        <% end %>
        <hr/>
      </li>
    <% end %>
    

What’s Going On Here?

  • We loop through each MailerSubscription instance. If it’s a new_record? we create a MailerSubscription. Otherwise, it’s an existing record and we toggle! the subscribed value.
  • In either case we use a button_to to hit the correct endpoint. Note that when we’re creating a new MailerSubscription we pass mailer_subscription.attributes as params, but we’re only permitting the mailer value in our controller.

http://localhost:3000/mailer_subscriptions

Page for User to Update Their Email PreferencesClick to expand

  1. Add shared logic to ApplicationMailer.

    # app/mailers/application_mailer.rb
    class ApplicationMailer < ActionMailer::Base
      before_action :set_user
      before_action :set_unsubscribe_url, if: :should_unsubscribe?
      before_action :set_mailer_subscriptions_url, if: :should_unsubscribe?
    
      after_action :prevent_delivery_if_recipient_opted_out, if: :should_unsubscribe?
    
      default from: 'from@example.com'
      layout 'mailer'
    
      private
    
      def prevent_delivery_if_recipient_opted_out
        mail.perform_deliveries = @user.subscribed_to_mailer? self.class.to_s
      end
    
      def set_user
        @user = params[:user]
      end
    
      def set_unsubscribe_url
        @unsubscribe_url = mailer_subscription_unsubcribe_url(@user.to_sgid.to_s, mailer: self.class)
      end
    
      def set_mailer_subscriptions_url
        @mailer_subscriptions_url = mailer_subscriptions_url
      end
    
      def should_unsubscribe?
        @user.present? && @user.respond_to?(:subscribed_to_mailer?)
      end
    end
    

    What’s Going On Here?

    • We add several action mailer callbacks to the ApplicationMailer in order for this logic to be shared across all mailers.
    • We call prevent_delivery_if_recipient_opted_out which will conditionally prevent the mailer from being sent if the user is not subscribed to that mailer. This is accomplished by setting mail.perform_deliveries to true or false based on the return value of @user.subscribed_to_mailer? self.class.to_s. Note that calling self.class.to_s will return the name of the mailer (i.e. MarketingMailer).
    • We call @user.to_sgid.to_s to ensure the the URL is unique and does not contain the user’s id. Otherwise a bad actor could unsubscribe any user from a mailer.
    • We conditionally call these callbacks with should_unsubscribe? to ensures we’ve passed a user to the mailer.
  2. Conditionally render unsubscribe links in mailer layouts.

    <%# app/views/layouts/mailer.html.erb %>
    
    <!DOCTYPE html>
    <html>
      ...
      <body>
        <%= yield %>
        <%= render "shared/mailers/unsubscribe_links" if @unsubscribe_url.present? %>
      </body>
    </html>
    
    <%# app/views/layouts/mailer.txt.erb %>
    <%= yield %>
    <%= render "shared/mailers/unsubscribe_links" if @unsubscribe_url.present? %>
    

Conditionally render unsubscribe links in mailer layouts.Click to expand