Haven't used Mandrill but in the past used the parent MailChimp a lot. While the service was great most of the time, when we ran into issues, MailChimp support

Haven't used Mandrill but in the past used the parent MailChimp a lot. While the service was great most of the time, when we ran into issues, MailChimp support sucked. It was hard to get issues resolved and often times they would not resolve the right issues in the first place. In my opinion, if you have a high amount of email transactions, I would not use MailChimp or Mandrill because they don't back up their service with a good enterprise level support.