To Backup Yahoo Mail Data into PST File Format? I would like to suggest you can also try MailsBackup Yahoo Backup Tool to backup Yahoo email Accounts folder to hard drive, PC or webmail.It offers to take backup Yahoo emails to PST, EML, MBOX, MSG, EMLX, PDF, HTML, CSV, ZIP, DOC, RTF, XPS, MHT, etc.Users can migrate Yahoo emails to Outlook, Gmail,- Outlook.com, Office 365, Exchange Server, etc.This tool enables user to backup multiple Yahoo Mail accounts without any limitations.