Yep. And one mistake can result in your server on blacklists it's not clear at all how to remove yourself for (sometimes the process is designed specifically for true bulk mailers and not small-fry "run your own email server" kinds of things).

Eg., set up an alias that forwards to gmail and do your best to make sure spam doesn't get forwarded to gmail and put your entire server on their blacklist? Probably you didn't do good enough.