Hello Mr. Berevoescu,

Here is an answer to your question.

Ethereum address is not case sensitive, thus, the lowercase ETH address in the Registration receipt is alright to use for you.

If you want to check if your lowercase ETH address works for you here is where you can verify it. https://www.etherscan.io/

Plus, how the service displays the ETH address is up to the service provider so that you do not need to worry about how the ETH address is displayed either in lowercase or in uppercase or mixed.

Reason why Ethereum address shown mixed with upper and lower cases when creating ETH address is in order to do ‘Checksum’ for inspecting ‘typos’ and this an additional function being added later by Ethereum.

If you have further question please feel free to ask me again(:

Thanks,

BOSAGORA TEAM