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I have a user who has e-mail dating back 8 years that are stored in a lot of different PSTs, about 15-20 different psts.

After opening 7 or 8 of them it starts giving Out of System resources error, however if you check Task Manager, the computer is no where near its page file limit. The only way to open more is to close a few and then restart Outlook.

So my question is: Is there some sort of known limit to the amount of PSTs Outlook can handle? And if so, is Outlook 2007 any better?

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Could it be that you used an 32 bit version of outlook which, as default 32 but windows app, can only use up to 2GiB? – Hennes Mar 2 at 11:14

There is not a documented limit to the number of PSTs one can attach to a profile, nor is there any documentation on the effects of multiple PSTs. There are some rumors which claims Outlook 2003 has a limit of 128 but I don't believe Microsoft has set a limit for that. The only limit they set is on size: By default, .pst files are in the Unicode format in Outlook 2007 and in Outlook 2003. Additionally, the overall size of the .pst files has a limit that is more than the 2-GB limit that is imposed by the ANSI .pst files. By default, the limit for a Unicode .pst file in Outlook 2007 and in Outlook 2003 is configured to be 20 GB.

For more info about PST size limits:

KB830336: The .pst file has a different format and folder size limit in Outlook 2007 and in Outlook 2003. KB832925: How to configure the size limit for both (.pst) and (.ost) files in Outlook 2010, Outlook 2007, and in Outlook 2003.

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I suggest you configure the size limit for PST files in Outlook 2003 by using registry.

For more information, you can refer to this KB article:

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