Office 365: Outlook & other MSO apps interaction

A curiosity, perhaps a setting somewhere, perhaps intentional by design.

I use Outlook client for my emails using outlook.pst for emails to my main email address, other .pst files for my other email addresses.

Assuming Outlook is not running, I've noticed that when I open another Office app, Word, Excel, PowerPoint, Publisher for example, a file ~outlook.pst.tmp is created, even if no document is opened. When I close the Office app that file is closed and disappears, and the modified date and time for outlook.pst is updated to reflect the time of app closure.

I can sort of understand it if I'd opened an Office document, especially one that had email links, but opening the .tmp file when purely opening the app seems perhaps odd.

Anyone know the reason for this?

I've found an Outlook option that when unset no longer causes MSO apps to touch outlook.pst.

In Outlook File/Options/People: Untick "Show user photographs when available"

Trying with both Word and Excel no longer touches the pst file.

I can't see any disadvantage in unsetting that option.

I'll mark this as solved now.

Hi Tony,

Thanks for sorting that out and sharing your solution.

I use a current version of Outlook that utilizes an ost data file instead of a pst file. I test launched both Excel & Word and they both changed the modified date to my ost file upon closing.


No doubt, someone at Microsoft has a very good reason for this feature, can't say I much care for it regardless.

I have also unchecked this box, I don't use people pictures on my PC.