There are several ways to upload PST files into Office 365, but users can use the most efficient method, which is named
SysTools Import PST to Office 365 Tool. With this dedicated migration utility, users can easily select PST files, authenticate their Office 365 account, and import emails, contacts, calendars, and other mailbox items directly into the target mailbox without dealing with complex configurations. Another feature of this application is that it also preserves folder structure, ensures data integrity, supports large PST files, and allows selective migration using filters.
To put it briefly, while Microsoft's manual methods are effective for admins, using this expert migration tool provides a more seamless, quicker, and easier way to upload PST files to Office 365—especially if you want successful outcomes with little work.