Set Message-Id with Mandrill for bulk emails
问题 I am sending emails to lists of contacts based on templates using Mandrill. I would like to track if the contacts have replied to my email and, to do so, I would like to check whether the Message-Id of my sent emails appears in the In-Reply-To header field of new messages. The problem is that I have to generate and set the Message-Id manually since Mandrill only gives me their internal _id . However, since I am sending emails to various contacts at the same time, I set preserve_recipients to