there is a software that easily backup your office 365 try this software it backup your office 365 in pst format and that have the option to backup to PST, MSG, EML, EMlx, and MBOX file format if want to backup other formats then uses it and available trial version. For more detail visit here:
Office 365 Backup - How to Get Easy and Fast Backup of Entire Office 365 Files
Office 365 Backup - How to Get Easy and Fast Backup of Entire Office 365 Files