Gmail Backup Tool is the most secure and powerful tool that helps to create a backup of Gmail to a hard drive. It can save Gmail emails to different files such as PST, PDF, CSV, MBOX, HTML, EML, MHTML, etc.  Moreover, it can also offer to convert Gmail to Office 365, Yahoo, Hotmail, Thunderbird, iCloud, etc. They are also competent enough to backup Gmail emails to the computer with entire mailbox items such as emails, contacts, calendars, etc. Additionally, it supports all versions of the Windows operating system. To explore the performance you can download it. 

However, if you want to convert your Gmail to Office 365 then you will go with this informative article Migrate Gmail To Office 365. This article will provide the most efficient and effective manual solution to migrate the process.