You can use the secure and reliable Yahoo Backup Tool to backup your entire Yahoo mailbox data. This software is well capable of converting your bulk Yaho emails into various file formats such as PST, PDF, EML, MBOX, etc. It also allows its users to skip the previously migrated items from the migration process. Moreover, users can also migrate their emails to Gmail, Yandex mail, AOL, Hotmail, and many other email clients. To analyze its performance, try its free demo version. 

However, In some instances, users also face sign-in problems with their Yahoo account. Therefore, to fix these issues, you can go through this informative article that I've recently explored. This article will provide you an in-depth guide od the manual method to fix Yahoo mail sign in problems. Additionally, it will also introduce you a software solution that will help you to timely backup your Yahoo emails.