if Yahoo is mail down for you then it is obvious that you are not able to access your Yahoo mail and also you become unable to sign-in to your Yahoo mail. But, you no need to worry about it, This issue is system generated and sometimes with a simple restart of your device helps you to resolve server problems, So you have to turn off your devices and wait for a minute then restart your devices, then the issue of down Yahoo mail will be resolved automatically.

For more info - https://onlinegeeks.net/is-yahoo-mail-down/