This is too bad. Mandrill was a great product I've put several clients and my own apps on. None of these have any use for Mailchimp integration. In December, they began to require the more strict DNS configs for new accounts... that was fine, but this latest change is horrendous in that it's giving business' who've used this service for years, an ultimatum... one that favors finding a new service. It's going to be wo…
Sounds like you're in the same boat as me. Just quickly tried out Mailgun and SendGrid today as alternatives. SendGrid looks more stable, but Mailgun has the advantage of at least being able to see subject lines in emails sent (which can be a great help when troubleshooting for clients).
There's one project we integrated a private messaging system deeply into their APIs. There's not gonna be a choice on moving that one, but all others will move.
Not sure if it's more greed or incompetence behind the flippant decision.