Is it permissible to close a friend's email account without his knowledge, after discovering its use in sins, and without the desire to inform him?

If you create an email account for your friend or give him one of your own private email accounts, the email becomes his property and responsibility. You are not permitted to view its contents or close it without his knowledge, due to the sanctity of a Muslim's property and honor. However, if you lent him the email account and he used it for unlawful purposes, then you are permitted to close it or advise him, because the email still belongs to you. It is recommended to advise your friend in both cases and explain the danger of sins.