Outlook on MacOS is taking a huge amount of space on my harddisk.

Thank you very much answering my questions. I did as you said check the online size (see image) and also checked the local folder size (see also image). The online storage is 17gb while the local storage is 88gb. That is a huge difference. Any advise how to reduce the local size is welcome.

Hi Conrad Hagemans

Thank you very much for your prompt reply and for providing the storage information. I appreciate your cooperation.

According to the details you shared, it appears that you have two Exchange accounts configured in Outlook, but I only see the online storage information for one account in your screenshot. To better assist you, could you please also provide the storage details for your second Exchange account?

If possible, please log in to Outlook Web for your other account and send me a screenshot or let me know the storage usage for that mailbox as well. This will help me get a complete picture and recommend the most suitable next steps for your situation.

Thank you again for your support and patience. Please let me know if you need any guidance on how to check the storage for your other account.

Of course. No problem. I just checked that one as well. It's a small account. See the screen image below.

Hi Conrad Hagemans, 

Have a good day and I hope you're doing well!

Thank you for your continued cooperation. 

To help reduce the local storage used by Outlook, I would like to guide you through safely clearing the cache folders. Please follow these steps carefully: 

1. Close Outlook completely. 
2. Open Finder on your Mac, then press Command + Shift + G. 
3. Enter the following path:

~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/Main Profile/ 

4. In this location, look for a folder named "Cache".  
5. Right-click on the "Cache" folder and select "Get Info" to check its size. This will help us determine if the cache is taking up significant space. 
6. If the "Cache" folder is large, you can safely delete its contents (or the entire folder if Outlook is closed). If you have more than one Outlook profile (for example, if you use two accounts), please repeat these steps for each profile and clear the "Cache" folder in both. 

Please note that: 

• Do not delete the entire "Data" folder or any of the blue folders inside it (such as Contacts, Messages, Mail Accounts, etc.), as these may contain important configuration or local data. 
• You should only delete the "Cache" folder (if present) or individual cache/index files (such as those ending with .sqlite, .shm, .wal, .db) inside the "Data" folder. 

If you are unsure about any step, or if you see multiple profiles and are not certain which one to clear, please send me a screenshot of the folder contents before deleting anything, and I will be happy to guide you further. 

If you find that the "Cache" folder is not taking up much space, or if your Outlook storage is still unusually large after clearing the cache, the issue may be caused by other hidden or corrupted files. 

In this case, I recommend uninstalling Outlook completely and then reinstalling it. This process can help resolve any persistent issues related to leftover data, corrupted profiles, or hidden cache files that are not removed by manual deletion. 

Caution: 

• Before uninstalling, make sure all your emails and important data are fully synchronized with the server. 
• If you have any local folders (such as "On My Computer"), please back them up, as these will not be restored after reinstallation. 

If you decide to proceed with uninstalling and reinstalling Outlook (or the entire Office suite), please refer to the official Microsoft instructions below:  Troubleshoot Office for Mac issues by completely uninstalling before you reinstall – Microsoft Support 

This guide provides step-by-step instructions to help you safely uninstall and then reinstall Office for Mac according to your Mac operating system.

Thank you again for your patience and cooperation. If you have any further questions or need additional support, please feel free to let me know. I am always here to help. 

If this answer was helpful, feel free to click "Accepted Answer" and give it an upvote. This helps me keep track of your case and continue supporting you as best I can. This also can make it easier for others facing a similar issue to find their way to a solution, too.

Wishing you a smooth and productive day!

Hi Conrad Hagemans, 

You can also try clearing the cache for individual folders in Outlook by following this official Microsoft guide: Clear the cache in Outlook for Mac. Just a quick reminder, please make sure all your important emails and data are fully synchronized with the server before clearing the cache, as any unsynced local data could be lost.