Error: Mandrill BCC Not Working

What's Causing This Error

Most possibly, Mandrill is ignoring the BCC headers and hence this error.

Solution - Here's How To Resolve It

To solve this,

1. Try using the To field rather than the Bcc field and set X-MC-PreserveRecipients to false.
2. Or else, specify the Bcc address in the To field but declare their type as bcc. Add "preserve_recipients": true under the message section. The code given below is an example of implementing this solution.

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{
   "to":[
      {
         "email":"to1.email@example.com",
         "name":"To Recipient Name",
         "type":"to"
      },
      {
         "email":"bcc1.email.@example.com",
         "name":"BCC1 Recipient Name",
         "type":"bcc"
      },
      {
         "email":"bcc2.email@example.com",
         "name":"BCC2 Recipient Name",
         "type":"bcc"
      }
   ]
}

Read more about X-MC-PreserveRecipients here.