Hi Igor thanks for posting in the Lucidchart Community! The feature you are referring to is Domain Control which you can learn more about in the Identity Management article in our Help Center. I am going to pass your request to our customer experience team who can help you. They will reach out to you shortly via email. 

For anyone else that would like to enable Domain Control on their Lucidchart Enterprise account please reach out via this form and we'd be happy to help you!