They are the opposite of a transparent organization - they are the GoDaddy of this business. (I was super pissed once they removed their status page..WTF). We hit these errors a few months ago with our clients and I put up a roadmap to move all of them off the terrible joke that Mandrill is, in under a month. None of my clients regretted the move.
I really don't miss anything about them and the market has caught up and they've been stagnant for way too long without any changes whatsoever and are still charging a premium for a prototype level quality of service.
If you're still using Mandrill in 2019, move out as soon as you can. I'm saying this with public interest as I had enough of these jokers.
[1] http://www.dangrossman.info/2016/02/28/mandrills-betrayal/
Edit: I built a Mandrill clone built on SES, Phoenix/Elixir and hosted on Google AppEngine which is basically Google's managed hosting service. I moved everything there and it works pretty well, planning to open source it at some point. The awesome thing about this is I can work on some specific features my clients want that isn't available on vanilla Mandrill.
I chose this route because I lost a lot of money with Mandrill compensating my clients for their fault, so I calculated that the money I lost over time would have been the same amount if I had invested in building a Mandrill clone myself. I plan to open source it at some point.