📎 AI Summary:
The thread discusses an issue in Outlook 2010 where the user’s email data file is a .pst instead of an .ost, and they cannot set this data file as the default because the option is greyed out. Respondents clarify that .pst files are typical for POP3, IMAP, and web accounts, and that Outlook 2010 doesn’t support .ost files for IMAP accounts. The original poster emphasizes that their main concern is why they cannot set their existing data file as the default, implying a desire for clarification beyond the technical distinctions. Overall, the discussion centers on account file types and configuration limitations in Outlook 2010.

quas

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Thread Author #1
I have a weird thing going on in Outlook 2010. It creates a .pst instead of .ost. I've no idea why. The problem is that I cannot set that .pst as the default data file. The option is simply greyed out.

I'm using Outlook 2010. Any ideas what's going on?

Thanks
 

Neemobeer

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That is normal behavior. pst files are used for POP3, IMAP and web based accounts. OST files are for Microsoft Exchange accounts.
 

quas

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Thread Author #3
Perhaps, but Outlook 2013/2016 creates only .ost databases for IMAP. But the more important question remains, why can't I set that data file as default?
 

Neemobeer

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Because Outlook 2010 doesn't support ost for IMAP
 

quas

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Thread Author #5
But that's not the answer to the important question, is it?