I discovered this trick a few days ago, and while I'm not sure if it's public or not, I don't see why I can't post this. Please note that you will still need to know the email address your account is connected to.
First, you're going to need a downloaded proxy. I use Hotspot Shield, so I don't know if anything else works.
Start up your proxy and use it, so that your IP is changed/hidden. Now, start up a Nexon game. It shouldn't matter which one, since I've tried on both Mabinogi and Vindictis and it worked fine.
Log in with the account you'd like to change. Or, at least try to. This is where Nexons hacking defences come in. It should depending on the game, it might say certain things, however you won't be able to log in.
Go to NEXON, and log into the website with the same info. The next screen should say that your account is locked for your protection and that it needs to be re-activated via email. Follow their instructions from there, disable your proxy, and enjoy playing, knowing that your account is safe.