The recipient's account has been blocked
If you sent an email from your Yandex mailbox and received a non-delivery report that states the following: “Policy rejection on the target address”, “Sorry, your message to <email address> cannot be delivered. This account has been disabled or discontinued”, “User account disabled for being inactive”, “Your email has been returned because the intended 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.