Add configuration

app/mailers/application_mailer.rb

@@ -3,5 +3,5 @@
 class ApplicationMailer < ActionMailer::Base
   layout 'mailer'
 
-  default from: Devise.mailer_sender
+  default from: Rails.application.config.noreply_email_address
 end

config/application.rb

@@ -35,6 +35,7 @@ module Partynest
 
     # Fully qualified domain name.
     config.site_domain = 'libertarian-party.com'
+    config.noreply_email_address = "no-reply@#{config.site_domain}"
 
     # ActionMailer previews
     config.action_mailer.preview_path = Rails.root.join('app', 'previews')

config/initializers/devise.rb

@@ -20,7 +20,7 @@ Devise.setup do |config|
   # Configure the e-mail address which will be shown in Devise::Mailer,
   # note that it will be overwritten if you use your own mailer class
   # with default "from" parameter.
-  config.mailer_sender = "no-reply@#{Rails.application.config.site_domain}"
+  config.mailer_sender = Rails.application.config.noreply_email_address
 
   # Configure the class responsible to send e-mails.
   # config.mailer = 'Devise::Mailer'

spec/requests/membership_applications/create_spec.rb

@@ -56,6 +56,7 @@ RSpec.describe 'POST /membership_applications' do
 
     specify do
       expect(ActionMailer::Base.deliveries.last).to have_attributes(
+        from:    [Rails.application.config.noreply_email_address],
         to:      [MembershipApplication.last.email],
         subject: I18n.t('membership_application_mailer.tracking.subject'),
       )