If Outlook is in active use, the size of the OST file can grow quite significantly, while the actual size of data in the file remains the same. The new version of the object is written to a newly allocated space, but the old version remains in the OST file as well. In other words, when you remove or modify a message, contact, reminder or meeting, the object is only marked as removed, but is not removed physically and remains in the OST file. It is impossible to use these blocks to fully recreate the original object, which is why they can be treated as junk.
blocks of data from earlier versions of messages, contacts, files and other objects.old versions of messages, contacts, files and other objects.The analysis revealed the types of data that are not carried over to the PST file after OST file conversion: Our engineers have analyzed the content of OST (source) and PST (destination) files. eml file cannot contain more than 1 email message. eml files are a common standard for storing and sending RFS 822 messages. Recovery Toolbox for Outlook do not support a recovering of contact groups yet.Outlook for Office 365, Outlook for iOS and Outlook for MacOS).