ruby-on-rails,http-headers,smtp,sendgrid,bulk-email
You are grabbing an array of ActiveRecord objects with @subscribers = Subscriber.where(activated: true) and passing that into the smtpapi header. You need to pull out the email addresses of those ActiveRecord objects. Depending on what you called the email field, this can be done with headers['X-SMTPAPI'] = { :to =>...
django,email,html-email,mandrill,bulk-email
Djrill attaches a mandrill_response attribute to each EmailMessage object as it's sent. See Mandrill response in the Djrill docs. So after you send the messages, you can examine that property on each object in the messages list you sent. Something like: # Bulk send send_result = connection.send_messages(messages) for msg in...