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In my server I can't break blocks neither place them if I don't have OP and it is very annoying to play with friends who cheat because I need to give them OP or they neither I can break or place blocks.
I tried setting spawn protection to 0, but it did nothing, please help me, I hate this 
Aternos account : Rid8
Do you have EssentialsX?
If yes, then it installs EssentialsProtect and EssentialsAntiBuild with it.
Go to your plugins folder and remove these plugins (they are unnecessary:)
EssentialsXAntiBuild
EssentialsXProtect
EssentialsXXMPP
