Hi, I had asked that question before, but good! When I asked recently, I forgot that is displayed in Minecraft (If I want to join server): "This access is only for friends" or something!
The setting:
Since friends can also make settings on the server.
What do you want to change in the settings? Without this info I can't help you
Well, that every x-Belieber can Joinen on it!
Is the whitelist activated?
As compi03 said, if you enter the account name of your friend's Aternos account there, he can edit the settings of your server.
By itself everyone can join your server (nobody will do it unless nobody knows the IP).
As you know for sure you have to enter the IP of the server in Minecraft in order to join it.
That's why nobody who does not know your IP can join the server.
But when I had recently tried to join it (after I had called ALL data correctly) I had 'ne connection… However, then stood there that only friends can join the server!
This means that you have a whitelist on it.