There are multiple servers where you can play The Mana World. Each server can run a different world. Different servers may be set up for different target languages, but also as an entirely separate projects. Below is a non-exhaustive list of available servers.
Security warning: Do not use the same username and password on two different servers. The server admins can read all of them in clear text and nothing stops them from trying them on other servers. It happened a lot in the past that users of the official server got "hacked" because they ignored this important precaution.
Address: server.themanaworld.org (port 6901)
Online player list, Registration
This is the official The Mana World server. The current client picks this as the default server. One thing to keep in mind is that since it's open to everybody, we ask you to speak English when around other people (other languages are fine in party or private chat, of course).
More servers can be found on the wiki Servers page. You may also advertise your own server there!