PayPal IPN Send Email - ruby-on-rails

Question

I have a controller that handles PayPal's IPN callback. I want to mark an attendee as 'paid' and send them a confirmation email if they've successfully paid.
The mark paid action is working but the email is not sending.
Here's my controller:
class PaymentNotificationsController < ApplicationController
protect_from_forgery :except => [:create]
def create
PaymentNotification.create!(:params => params, :attendee_id => params[:invoice], :status => params[:payment_status], :transaction_id => params[:txn_id])
if params[:payment_status] == 'Complete'
#attendee = Attendee.find(params[:invoice])
## Working
#attendee.update_attribute(:paid, Time.now)
## Not Working
UserMailer.welcome_email(#attendee).deliver
end
render nothing: true
end
end
Here's my user_mailer file:
class UserMailer < ActionMailer::Base
default from: 'example#email.com'
def welcome_email(user)
#user = user
email_with_name = "#{#user.first_name} #{#user.last_name} <#{#user.email}>"
#url = 'http://example.com'
mail(
to: email_with_name,
subject: 'Welcome to Yadda Yadda'
)
end
end
Here's the weird thing, in another controller that doesn't have PayPal the mailer works:
class VendorsController < ApplicationController
def create
#vendor = Vendor.new(vendor_params)
if #vendor.save
UserMailer.welcome_email(#vendor).deliver
redirect_to vendor_success_path
else
render 'new'
end
end
end

Answer 1

I am pulling your answer out of your question and posting it here for future reference.
This takes two actions (mark paid and send mail). It has been moved to the model as an after_create method.
Here's the model:
class PaymentNotification < ActiveRecord::Base
...
after_create :mark_attendee_paid
private
def mark_attendee_paid
if status == 'Completed'
attendee.update_attribute(:paid, Time.now)
UserMailer.welcome_email(attendee).deliver
end
end
end