```ruby
class ApplicationMailer < ActionMailer::Base
  # TODO: Remove hard code domain
  default(from: Rails.application.config.action_mailer.smtp_settings[:from],
          "Message-ID" =>"#{Digest::SHA2.hexdigest(Time.now.to_i.to_s)}@noty.im")

  layout 'mailer'
end
```

Switch to lambda to avoid same mesage id
user
```ruby
class ApplicationMailer < ActionMailer::Base
  # TODO: Remove hard code domain
  default(from: Rails.application.config.action_mailer.smtp_settings[:from],
          "Message-ID" => lambda {"#{Digest::SHA2.hexdigest(Time.now.to_i.to_s)}@noty.im" })

  layout 'mailer'
end
```
assistant