Example Mandrill message send call - to demonstrate code for preserve recipients.

Mandrill preserve recipients false

response = MANDRILL.messages_send(
      message: {
        html: email.body,
        subject: email.subject,
        from_email: email.from_email,
        from_name: email.from_name,
        to: email.recipients.map{|recipient| {email: recipient}},
        preserve_recipients: false,
        auto_text: true,
        inline_css: true,
        track_opens: true,
        track_clicks: true
      },
      async: true,
    )

Example request body:
key=[KEYHIDDEN]&
options[track_opens]=true&
options[track_clicks]=true&
message[html]=hello test.&
message[subject]=test To&
message[from_email]=[EMAIL1HIDDEN]&
message[from_name]=[NAME1HIDDEN]&
message[to][0][email]=[EMAIL2HIDDEN]&
message[to][0][type]=to&
message[to][1][email]=[EMAIL3HIDDEN]&
message[to][1][type]=to&
message[preserve_recipients]=false&
message[auto_text]=true&
message[inline_css]=true&
message[track_opens]=true&
message[track_clicks]=true&
async=true

API log:

Full Request
{
"key": "REDACTED",
"options": {
"track_opens": "true",
"track_clicks": "true"
},
"message": {
"html": "test 2",
"subject": "test 2",
"from_email": "REDACTED",
"from_name": "REDACTED",
"to": [
{
"email": "REDACTED"
},
{
"email": "REDACTED"
}
],
"preserve_recipients": "false",
"auto_text": "true",
"inline_css": "true",
"track_opens": "true",
"track_clicks": "true"
},
"async": "true"
}

Full Response
[
{
"email": "REDACTED",
"status": "queued",
"_id": "1b05218290244bb19dc5ed7f8274dd04"
},
{
"email": "REDACTED",
"status": "queued",
"_id": "fe46f28df30b43c194908a234223e369"
}
]