If are you looking best tool for importing PST files to Office 365 you can try this Aryson PST File Converter Tool. This tool is the most efficient tool for importing PST files to Office 365 and many more email clients such as Outlook PST email to Thunderbird, Gmail, IMAP, Hotmail, Yahoo, & Opera Mail successfully. It also can convert PST, to EML, PDF, TXT, MSG, MBOX, HTML, EMLX, MHTML, etc., file formats with ease. It maintains the folder hierarchy during conversion as per the browse PST file structure.

If you want to learn how to export Outlook contacts from OST to vCard/VCF format, use the professional solution ToolsBaer For Address Book Manager Software. This application is among the best for finishing the process fast and in a few simple steps. It works with all Windows editions, including XP, Vista, 7, 8, 8.1, 10, and later updated versions. On top of that, it can convert Outlook OST files from any version—2019, 2016, 2013, 2010, and earlier editions—to another format. The tool can also split and merge VCF connections without the need for any further software. To access further features, download the free trial version of this application.
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If you're dealing with oversized Outlook PST files, splitting them into smaller files is definitely a good practice to improve Outlook performance and reduce the risk of corruption. One option that's worked well for bulk PST management is the DRS Softech Outlook PST Splitter. It lets you split PST files by size, date, folder, or email ID while preserving the original folder hierarchy and metadata. It also supports both ANSI and Unicode PST files and offers a demo version if you want to evaluate it first.