OST is a native file for Windows Outlook but you cannot use it for importing data manually. For all such purposes, there is PST. Therefore, if you are looking to import or upload OST to Office 365 Outlook client, it may not be a simple and straightforward task.
Upload OST to Office 365
The only way forward is to convert the file to PST using a third-party tool. But most such software tools do not have the enough features to make it efficient for an advanced user or has a simple interface to make it doable for a basic user. Most of all, these tools do not convert the data from files accurately. You are bound to find many items like graphics or attachments missing.
The task of converting OST files to PST to upload it to Office 365 Outlook proves to be extra difficult if the files involved are too large. Mostly, users who have been using Outlook for a long time have generally reached to a point where the OST file is huge. Converting that to PST using a generic solution is not only efficient but risky as well.
Tool to Upload OST to Office 365
That is the reason USL Software threw away all the typical methods for data processing during the conversion of these files. They developed a new tool from scratch that can handle all the complex information with precision and not output files full of integrity errors. The result is “OST Extractor Pro,” a powerful and adequate software that can get this job done effortlessly.
You can upload OST to Office 365 by converting the ost file into PST file formats. The PST is supported by both Mac and Windows Office 365
OST Extractor Pro

One of the most impressive feats of USL Software is to make it a simple enough converter for home users without compromising with power. It is the only OST to PST converter that is fitting in all scenarios, from large to small scale data conversion projects. Whether you have personal OST files to convert at home or massive corporate files in a work-place, this is exactly what you need.

The dedicated system for each complex component of files yield results free of errors. Every little graphical component, attachment files, email addresses in Unicode languages, or headers in MIME format – everything is safely processed from OST to PST.
And then, you can very easily import those PST files to your Office 365 Outlook client.
How to Upload OST to Office 365
- Get ‘OST Extractor Pro’ for Mac or Windows.
- Open it and click on “Add OST”
- Browse and select ost file.
- Check Optional settings
- Select PST File as your output format.
- Click on “Convert”
- Then upload the converted PST file into Office 365.
The nature of PST files also gives you additional benefit of using them in both Windows and Mac version of Outlook.
“OST Extractor Pro” also takes care of tiny annoyances that often come up during the job. These can be small frustrations or at times can also prove to be detrimental to the overall result.
Get it to upload OST to Office 365
You can find all about those features and options in a free trial version. The only difference between a trial and a full version is that in trial you get to convert up to ten items per folder, while in a full version, there is no such limitation. You can download it using the instant direct link below.
Download Now at https://www.uslsoftware.com/download/ost-extractor-pro/
OST Extractor Pro is not only help you to upload OST to Office 365, but also converts OST file to other file formats including Apple Mail, Mozilla Thunderbird, Postbox, MBOX, EML etc.