Set Email Message ID for Devise confirmation emails

Question

All the devise confirmation emails are going to spam folders, and this question suggests I need to set the message-id for default UserMailer. How would i set the default for devise's confirmation emails?

This is the code to set it

require 'digest/sha2'
class UserMailer < ActionMailer::Base
  default "Message-ID" => lambda {"<#{SecureRandom.uuid}@#{Rails.application.config.mailgun_domain}>"}

  # ... the rest of your mailer class
end

Answer 1

Patching the DeviseMailer should work

app/mailers/devise_mailer.rb

class DeviseMailer < Devise::Mailer
  default "Message-ID" => lambda {"<#{SecureRandom.uuid}@#{Rails.application.config.mailgun_domain}>"}
  ## ...
end

config/initializers/devise.rb

Devise.setup do |config|
  config.mailer = 'DeviseMailer'
  # ...
end