How to attach an attachment in the logstash output email

[kc55]

Hi all,

In the guide format , they said the attachment is using array.
However after the format and it seems the email has been sent but no attachment in it.

output {
if "shouldmail" in [tags] {
    email {
      to => 'technical@example.com'
      from => 'monitor@example.com'
      subject => 'Alert - %{title}'
     body => "Tags: %{tags}\\n\\Content:\\n%{message}"
     template_file => "/tmp/email_template.mustache"
     domain => 'mail.example.com'
     attachment => ["C:\picture.jpg"]
     port => 25
    }
  }
}