To delete a mail.ru mailbox, you need a user who knows the password from him to follow the link:
http://e.mail.ru/cgi-bin/delete
and follow the instructions on the screen.
Together with the mailbox, all services will be deleted, Photo@Mail.Ru, Blogs@Mail.Ru, etc.
You can restore the mailbox address in the future, for example, by receiving an SMS via an attached mobile phone.