> - You need to make sure that your email servers IPs are not on black lists.

This alone is a huge, huge chore. Especially if you run a hosted service that allows some user-specified content in outbound email bodies. It's a lot cheaper for us to pay Mandrill to handle all of that for us, provide us excellent metrics and diagnostics, and let us know if one of our users is sending junk mail before it gets out of hand.

Even if you do everything right you can still find yourself on a blacklist. Then you get to pound sand.

Blacklists suck. Not as much as spam sucks, though.

Frankly, with the amount of bullshit blacklists out there that real mail providers actually trust, I've come to detest blacklists more than spam.

Has anyone set up a blacklist full of random IPs as a joke to see how many people follow it?

Well, we have been put on blacklists that the operator wanted money to "expedite" removal from. I'm assuming that blacklist was pretty much random IPs... And it did impact deliverability.