1547 - PST file is smaller than backup size shown

Symptom

A PST file that is downloaded as part of an Exchange mailbox recovery is found to be smaller in size than the backup size shown in the RedApp. 

Cause

This is expected behaviour and is due to two reasons:

• The PST file's data is compressed.
• Redstor stores the complete Microsoft FTS data at the point of backup, but we omit some unnecessary data when generating the PST restore file.

For more on PST imports, see this Microsoft article.