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We run Exchange 2003 and we have a user who is cleaning out some files from his machine. We ran into a file called x_Outlook.pst_x. I was not able to find anything on Google about it. Does anyone know what this file is? Is it a backup of a .pst file? The file is actually quite large. I think almost 2GB.

Any help or insight would be greatly appreciated.

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Perhaps it's a backup .PST file? I haven't seen any references to anything like that after a few Google searches. – Isxek Nov 2 '10 at 14:07
Did you once run a setup where users had their e-mails stored on their local machines? I'm pretty sure with Exchange it runs .ost files and PST are locally stored files. I also think it will be a human made backup, perhaps when you transitioned over to exchange if it was recent? perhaps as it reached the size limit? One way to find out.... Import the file and have a look – Joe Taylor Nov 2 '10 at 16:23

This smells like a hand-made backup of the main pst. The pattern of extending the filename with x_ and _x smells like human behavior and not like a backup made by a program (of any sort).

Also check the date of the file, that might give you a clue what's up with it.

Edit: As Randolph Potter pointed out, it might be a hand-made archive, because it was approaching (or has hit) the maximum size for a pst file, it might also be corrupt. If you're very adventurous, you could try to import it in to a clean Outlook-Installation and see what's inside and to who it belongs.

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Yup, agreed. It was probably created because it was approaching 2GB in size, which used to be the maximum allowable size for PST files. It may even be a corrupt file because it did get to that fateful 2GB limit. – user3463 Nov 2 '10 at 15:12

It looks more like user created file.

You have two options.

  1. Rename the file to pst and try to open this file in outlook and see if works.

  2. Otherwise, the big size file might be a media file. You can check the same using the utility called mediainfo (

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