Ping URL for Mandrill with membership plugin

I saw the instructions to set the ping url for Mailchimp from membership plugin

Ping URL - http://us2.api.mailchimp.com/1.3/
Ping data -

method=listSubscribe
apikey=mykey
list=listid
email_address=%useremail%
send_welcome=true
update_existing=true

"Strip query strings from URL" - GET

QUESTION-
What PING URL do I use for MANDRILL, which is Mailchimp's transactional emails.