Microsoft Outlook stores all the email messages and other mailbox data in an Outlook data file, known as PST or personal storage table. In the earlier versions of Outlook, i.e. from 97 to 2002, Outlook creates PST file in ANSI format. In MS Outlook 2003 and later versions, PST files are saved in Unicode format. The major difference between these two formats is their size limitation. ANSI PST is an old format and can store mailbox data up to 2 GB. While Unicode PST has a maximum size limitation of 10 GB to 50 GB. If this specific mailbox size goes beyond the limitation, the Outlook data file may become prone to corruption. Compared to Unicode format, the chances for corruption in ANSI PST files are fairly high. Having a large amount of mailbox data will definitely increase the size of your PST file. If it is not controlled, it may exceed the size limit and may result in corruption.
To avoid corruption in PST files due to size limitation problem, you can reduce the file size by using Outlook’s Compact feature. This is an easy and effective way to reduce PST file size. Also, you can remove all the unwanted email messages, duplicate items, heavy attachments and other mailbox data from the PST files to get enough free space.
Unluckily, if your PST file is corrupted due to a size limitation problem or other reasons, you can try the Inbox Repair tool of Microsoft Outlook aka SCANPST.EXE to scan corrupt PST files for errors and to repair Outlook PST files. It is a built-in tool in MS Outlook that effectively works with corrupt Outlook data files.
Read How to use the Inbox Repair tool to recover email messages in Outlook?