In order to close your old Yahoo-mail account,take proper steps to save your information and all necessary data inside the account. Firstly, log in to your Yahoo-mail account and check on box option ” Keep me signed in”. Cancel all your subscriptions and Send message to all your Contacts that you are now closing your email account. If you’re registered with Microsoft Account, then you may have OneDrive or Office 365 subscriptions. Go directly to to your  microsoft account and open “Services and subscriptions” and cancel all subscriptions from there. If you are still receiving email after closing your account,follow these steps:

• Go to settings, and Open Accounts, and go to “Managing your account” section and select this option “Email forwarding”.
• Add new email address here. In the same field, you can also choose, “Sending automated vacation replies”. 
• Now go to the support page in email service, and press Ctrl+F to search for “delete my account”, Follow instructions there and Delete your account after typing your password. Choose one list of reason of closing your account.
• Finally submit Your confirmation.