There were a lot of people at CiviCon Denver at the dev ops session using Mandrill for bulk email.  I'm not one of them so don't have a config to share, but can confirm that some very experienced providers use it. It was more popular than CiviSMTP or Amazon SES. The only one I recall specifically is CiviDesk, who praised the ability to use sub accounts to track their clients' usage separately. Shoot them an email perhaps?