400+ GB system data

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Level 1

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400+ GB system data

By scrolling thru the various libraries & containers in with Finder, I've identified 169 GB of the 400 GB (320 GB, 370 GB 425 GB keeps changing) in Library>UBF8T346G9.Office and about 165GB is the subfolder UBF8T346G9.Office>Outlook. I'm afraid to delete the contents of these subfolders because I don't know what I'm deleting. My Outlook app shows about 7 GB stored on disk and lists all the "outlook" folders and sizes where emails are stored. If I have only 7 GB or so of emails & attachments, what's the other 160 something GB's? Is it safe to delete it?

Thanks,

MacBook Pro 13″, macOS 15.6

Posted on Nov 1, 2025 11:48 AM

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Answer 1

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steve626

Level 6

13,389 points

Nov 1, 2025 6:17 PM in response to sevencrows

sevencrows wrote:

By scrolling thru the various libraries & containers in with Finder, I've identified 169 GB of the 400 GB (320 GB, 370 GB 425 GB keeps changing) in Library>UBF8T346G9.Office and about 165GB is the subfolder UBF8T346G9.Office>Outlook. I'm afraid to delete the contents of these subfolders because I don't know what I'm deleting. My Outlook app shows about 7 GB stored on disk and lists all the "outlook" folders and sizes where emails are stored. If I have only 7 GB or so of emails & attachments, what's the other 160 something GB's? Is it safe to delete it?

Thanks,

If you delete anything in that Office directory, it is likely that Outlook and the calendar will stop working. Outlook will lose its index and not be able to find emails and calendar items.

Some of that storage could be associated with the Calendar, or possibly with the Sent and Deleted email folders. Have you emptied the trash (Deleted folder) in Outlook? Do you ever pare down your Sent folder? Sometimes these folders can grow huge over time. Depending on how Office is implemented on your server, there can be a large Online Archive which, if mirrored on the computer, can be huge.

How are you measuring the size of your Outlook folders? Are you using the Properties option?

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Answer 2

sevencrows Author

Level 1

4 points

Nov 2, 2025 4:49 AM in response to steve626

Above are 2 screenshots from Outlook properties. I don't see any way of exporting the entire list, but you can see from the screenshots that my inbox is about 1.9 Gb, and the only other folder with more than a gigabyte is my Groupwise archive at about 4 Gb. The total shows 7 Gb, so all the other folders add up to 1.1 Gb. My Onedrive is showing about 13 Gb on disk, but that does not appear to be included under the Library>UBF8T346G9.Office container. Also, there's a "data" folder Library>UBF8T346G9.Office>Outlook>Data (30.3 Gb) that includes folders for calendar, contacts, etc.

I've shutdown and restarted in Safe mode, and then restarted again as someone suggested but no significant changes. I have not tried reindexing Spotlight, but I may try that next. Any suggestions?

Thanks for your assistance.

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Answer 3

AlWeir

Level 5

4,580 points

Nov 1, 2025 2:32 PM in response to sevencrows

A Good Article On What Ststem Data Is

What is System Data in Storage Settings?

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