Does anyone know if Outlook has solved the problem of data file size ?

Hi,

By default, Personal Folders (.pst) and offline Outlook Data File (.ost) files are in Unicode format in Microsoft Outlook 2010 and Outlook 2013. The overall size of .pst and .ost files has a preconfigured limit of 50 GB. The Outlook file size limit of 50 GB can be increased or decreased by making changes to the Windows registry.

HKEY_CURRENT_USER\Software\Microsoft\Office\xx.0\Outlook\PST

DWORD: MaxLargeFileSize   (This value controls how many MB a user can write to a pst-file.)
DWORD: WarnLargeFileSize  (This value controls how many MB the system can write to a pst-file)Value: Enter a decimal value in MB.

For detailed information, please have a look at the following KB article:

https://support.microsoft.com/en-us/kb/832925

However, it's not recommended to set the limit to a larger size. It will be hard to repair the Outlook data file if it is too large, and it will increase the risk of lossing data.

Regards,

Steve Fan
TechNet Community Support