If you sent an email from your Yandex mailbox and received a non-delivery report: “Policy rejection on the target address”, “Sorry your message to cannot be delivered. This account has been disabled or discontinued», «User account disabled for being inactive», «Your emails has been returned because the intented recipient's email account has been suspended. The account must be re-activated to receive incoming messages”, this means that the recipient's account is blocked by the recipient's mail service.
Try contacting the recipient by another method and report the problem.