Microsoft Outlook stores all the data in a single file known as Personal Storage File (PST). In other words, it is a data file used for the storage of Outlook e-mail objects, such as contacts, attachments, appointments, contacts, journal, tasks, events, etc. Each version of Outlook has a different format. These formats are of two types- ANSI and UNICODE. Versions prior than Outlook 2002 uses American National Standards Institute (ANSI) format whereas later versions of Outlook employs UNICODE format.
Along with different format, different size limit has also been set by Microsoft. Once the set size limit gets exceed, an addition of no more data is allowed in a PST file.
Size limits for different versions of Outlook:
Once the Outlook PST file approaches the set size limit, it fails to add more data in it. Moreover, Outlook starts behaving abruptly and can even get corrupt. So, it is always advisable not to store unwanted data of Outlook e-mail objects in a PST file.
Note: If your PST file is already corrupt, you can repair it using >Outlook PST Repair.