Thanks for that link, LakeRat. I posted a comment there because I've also recently resurrected an old inquiry about getting an email API.
@dasfiend: I think we'll need to go somewhere else for an email API, while keeping other services here of course.
But as I said in my other comment, it doesn't matter what service we use, all services are subject to the whims of RBLs. The more sites there are on any shared host, the less reputable it looks, and the less reputable a server looks, the higher the chances of it getting shutdown. The only real "solution" is to manage your own server. Then again, if an RBL shuts-down your entire IP block (a.b.c.*) you're completely shutdown with no up-line vendor to help you argue your case to the RBL service desks.
So to my knowledge, right now there are no good solutions for this.