Microsoft Outlook has limits to how big the mailbox size (PST file or Personal Folders file) can be. This differs from version to version, so I’ll give a breakdown here:
Outlook 2002 and older
Outlook 97, 2000 and 2002 store messages in US English format. All emails, including foreign language emails, are saved in the Outlook PST file in that format. The PST file size is hard-wired to a maximum of 2GB. This limit cannot be changed.
Outlook 2003 and 2007
Outlook 2003 and 2007 store messages in a Unicode format, meaning virtually all characters can be used. The PST file in these versions of Outlook are preconfigured to a maximum of 20GB. Unfortunately this can’t be changed either. If you want to open larger files from later versions of Outlook you must reduce the size of the PST file to less than 20GB first.
Outlook 2010 and 2013
Outlook 2010 and 2013 also store messages in a Unicode format. The Outlook PST file is set to a maximum size of 50GB. This can actually be increased by making some edits in the Windows registry.
When Outlook PST files get close to their maximum size you will likely notice performance problems, although the performance degradation is due primarily to the number of emails you have in the PST file as opposed to the physical size of the PST file. You will likely also start to notice corruption of the file. It’s best to archive all of your old items, which will put them into a separate PST file to keep the size of your mailbox Personal Folders file down. Another way to keep the size of Outlook’s PST file down is to empty the deleted items and Junk folders regularly. If you need help contact us. 705.739.2.FIX (349).