I do not know if the servers I have tried are just out of date or not though (new updates last night and this morning after all).
If you are new and not just having an update issue, then be aware that many servers will only allow authenticated players to join (i.e. you need to have the launcher log you in) to cut down on people who would otherwise abuse the ability to log in with any name (i.e. including those of another player, or particularly an admin).