If you want to read messages in postal box Yahoo one by one, the default service settings are not ideal. Every time , when you delete or file messages, it sends you back to your Inbox only, to open the next message.
Luckily, you can avoid this extra step and have Yahoo Mail automatically jump to the next message after you’re done with the one you’re reading.
These instructions apply to the current version of Yahoo Mail for the web. This feature is currently not available in the Yahoo Mail app.