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Involute's avatar
Involute
Copper Contributor
Jan 23, 2025

What to do about an out-of-date .ost file?

I'm upgrading the SSD in my laptop, so I cloned the old one onto a bigger one and swapped them.  Windows (finally) boots fine, with all my apps intact.  When I launch Outlook however, it tells me it's using an old copy of my data (.ost) file, that I should exit Outlook, delete the .ost, and then relaunch.  Outlook will then create a new one.  I think this happened because it was a few days between making the clone and getting it to boot.  This is my backup PC, though, and Outlook on my desktop (main) PC is up-to-date.  Should I just copy that one over?  If so, where do I find it?  A search for all the .ost files on my PC yields 41 matches.  How do I identify the right one?  Thanks for any tips.

  • Just delete the ost file as recommended then restart Outlook. It will rebuild an up to date ost very quickly.

    The ost file shouuld be in folder "C:\Users\<username>\AppData\Local\Microsoft\Outlook\" unless you have moved it.

     

     

  • >> A search for all the .ost files on my PC yields 41 matches.  

    The ost name is alias@domain format at C:\Users\%username%\AppData\Local\Microsoft\Outlook\ - if you have multiple ost files with the same name and a number following the name, delete all. 

     

    You do not need to delete the account and add it back (you could, but need to set up signatures again), just close outlook, delete the ost files and restart outlook. 

  • CallThatGirl2's avatar
    CallThatGirl2
    Brass Contributor

    OST files are like a copy of all of your online data from IMAP or Exchange mailboxes. You don't need them unless you have data not on the server. Make a new Outlook profile and a OST will be recreated. 

  • JerryF1950's avatar
    JerryF1950
    Copper Contributor

    Just delete the ost file as recommended then restart Outlook. It will rebuild an up to date ost very quickly.

    The ost file shouuld be in folder "C:\Users\<username>\AppData\Local\Microsoft\Outlook\" unless you have moved it.

     

     

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