You need to import OST to Office 365. I recommended the ToolsCrunch Mac OST to PST Converter Tool easy to convert OST files into PST file format and PST files are directly Import Office 365 Account This process is very easy for any user. This application works very fast and safe conversion. OST file Properties such as email, notes, events, contacts, calendars, drafts, tasks, journals, attachments, etc. The software includes a user-friendly interface that allows users to perform the conversion process without any technical assistance. This application supports all Mac and Windows OS versions. Download the free demo version of the software.

Visit here: - https://www.toolscrunch.com/mac-ost-to-pst-converter.html

If you are exploring the comfortable method of converting OST to Office 365. Then you can go for Softaken Exchange OST to Office 365 Migration tool. With the help of this software, you can export OST files to Office 365 without any errors. This tool has users friendly interface you can thoroughly utilize its overall programming. Whereas if you’re unsure about this software then in that situation you can go ahead with its trial version before you purchase this software officially from its official site. Moreover, you can Step forward toward key features- This help of this software is capable to Export only selective OST files. It can maintain your data structure after the conversions. You can export both the archive and new OST files.OST files. You can smoothly convert oversize OST files to Office 365. This application is compatible with, Window10, XP, VISTA, 8, 7.

To import OST files into Office 365 or import PST files into Office 365, you can use Shoviv OST to Office 365 Migration tool (aka Shoviv PST to Office 365 Migration tool) This tool works well with corrupted and non-corrupted OST/PST files and import them into Office 365, Live Exchange Server, new PST, EML, and MSG.

I want to recommend to all users to go for a convenient solution MailsDaddy OST to Office 365 Migration Tool to shift the Exchange Server OST file database into Office 365 platform. It helps to import OST file data, like - emails, contacts, calendars, appointments, and attachments, etc into Office 365 environment. Here users can also upload multiple MS Outlook OST files into one or more Office 365 accounts using different searching options.
It is also compatible to import OST files into Microsoft PST format without any changes in original content. It provides impersonation and bulk export features that enable users to shift one or more OST file into different Office 365 account at one time. It has the capability to import OST files into Cloud 365 Primary and In-Place Archive mailbox.
To know more, visit here: OST to Office 365 Migration

Use OST To PST Converter is the most effective and efficient software capable of converting OST files to PST format. This utility is fully loaded with highly advanced features considering the requirements of high-tech users. Moreover, with the help of this tool, you can also convert OST files to different file formats and several email clients. It has an impressive graphical user interface that ensures a smooth working process without any technical expertise. Additionally, it supports all versions of the Windows operating system. You can try the trial versions of the software to explore the performance

To import an OST file into Office 365, you'll first need to convert it to a PST format using a reliable third-party tool. Next, access your Office 365 account and utilise the built-in Import service within the Microsoft 365 admin centre. Set up a quinque import job, upload the converted PST files, map them to the respective mailboxes, and initiate the import. Monitor the progress, and once completed, verify the data transfer. Remember to follow Microsoft's official guidelines for a seamless and secure import process.