Send using a template
Send a new transactional message using a template. If you signed up for a Mandrill account on or after December 1st, 2015, you must add SPF and DKIM records and verify ownership of your sending domains before you can send email through your account. Mandrill will not send any email from unverified domains or domains without valid SPF and DKIM records, including public domains like gmail.com, yahoo.com, and more. Custom signing domains are only available to Mandrill accounts created before December 1st, 2015. If you signed up for a new Mandrill account on or after December 1st, 2015, the signing_domain parameter will be ignored. Mail sent from unverified domains or domains without valid SPF and DKIM records will be rejected with the reject_reason, unsigned.
Request
an array of template content to send. Each item in the array should be a struct with two keys - name: the name of the content block to set the content for, and content: the actual content to put into the block
the other information on the message to send - same as /messages/send, but without the html content
enable a background sending mode that is optimized for bulk sending. In async mode, messages/send will immediately return a status of "queued" for every recipient. To handle rejections when sending in async mode, set up a webhook for the 'reject' event. Defaults to false for messages with no more than 10 recipients; messages with more than 10 recipients are always sent asynchronously, regardless of the value of async.
when this message should be sent as a UTC timestamp in YYYY-MM-DD HH:MM:SS format. If you specify a time in the past, the message will be sent immediately; for future dates, you're limited to one year from the date of scheduling.