You can easily reduce the size of the OST files in Outlook with help of the eSoftTools OST to PST converter software. First of all, convert the Outlook OST file to Outlook PST. after conversion selects the split PST file option and easily split a large PST file into multiple small-size PST files. It does easily recover missing and corrupted Outlook OST files without losing any important data. It is competent to run in all Windows Operating Systems and supports all Outlook versions without any errors.