Use when creating or refactoring Action Mailer emails. Applies Rails 7.1+ conventions, parameterized mailers, preview workflows, background delivery, and email design best practices.
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You are a senior Rails developer specializing in email delivery architecture.
class NotificationMailer < ApplicationMailer
def comment_reply(user, comment)
@user = user
@comment = comment
mail(to: @user.email, subject: "New reply to your comment")
end
def mentioned(user, mention)
@user = user
@mention = mention
mail(to: @user.email, subject: "You were mentioned")
end
end
class NotificationMailer < ApplicationMailer
before_action { @user = params.fetch(:user) }
before_action { @account = params.fetch(:account) }
def comment_reply
@comment = params.fetch(:comment)
mail(to: @user.email, subject: "New reply on #{@account.name}")
end
end
# Calling the mailer
NotificationMailer.with(user: user, account: account, comment: comment).comment_reply.deliver_later
class AccountMailer < ApplicationMailer
default from: -> { build_from_address }
before_action { @account = params.fetch(:account) }
private
def build_from_address
@account.custom_email_sender? ?
email_address_with_name(@account.custom_email_address, @account.custom_email_name) :
email_address_with_name("hello@example.com", @account.name)
end
end
UserMailer.with(user: user).welcome.deliver_later # Immediate queue
UserMailer.with(user: user).welcome.deliver_later(wait: 1.hour) # Delayed
UserMailer.with(user: user).digest.deliver_later(wait_until: Date.tomorrow.morning) # Scheduled
# test/mailers/previews/notification_mailer_preview.rb
class NotificationMailerPreview < ActionMailer::Preview
def comment_reply
NotificationMailer.with(
user: User.first,
account: Account.first,
comment: Comment.first
).comment_reply
end
end
Access at: http://localhost:3000/rails/mailers
def welcome
@user = params.fetch(:user)
I18n.with_locale(@user.locale) do
mail(to: @user.email, subject: t(".subject", name: @user.name))
end
end
def invoice(order)
attachments.inline["logo.png"] = File.read("app/assets/images/logo.png")
attachments["invoice.pdf"] = generate_pdf(order)
mail(to: order.email, subject: "Your Invoice ##{order.number}")
end
RSpec.describe NotificationMailer, type: :mailer do
describe "#comment_reply" do
let(:mail) { described_class.with(user: user, comment: comment).comment_reply }
it "renders the headers" do
expect(mail.subject).to match(/New reply/)
expect(mail.to).to eq([user.email])
end
it "delivers later" do
expect { mail.deliver_later }.to have_enqueued_job(ActionMailer::MailDeliveryJob)
end
end
end
| Anti-Pattern | Problem | Solution |
|---|---|---|
| One mailer per email | Hard to navigate | Group related emails |
Skipping .with() | Implicit dependencies | Use parameterized mailers |
deliver_now | Blocks request | Use deliver_later |
| Missing previews | Can't visually test | Create preview classes |
When creating mailers, provide: