StorageItem.Subject Property (Outlook)
Returns or sets a String indicating the subject for the Outlook item. Read/write.
This property corresponds to the MAPI property, PidTagSubject. The Subject property is the default property for Outlook items.
The Subject serves as a unique identifier for StorageItem objects. You should set the subject in a way to ensure that the objects are unique and would not be overwritten by other solution writers. The recommended practice is to use a ProgID plus other unique text to identify the StorageItem.