Outlook on MAC taking up lots of Space

If the space issue is directly related to MS Outlook

What is “Other” storage on a Mac, and how can I clean it out?

On my 2017 15” MBP, for example, Disk Inventory X, shows that the major culprit for using space is Microsoft Outlook data, which is buried several nested folders deep in the ~/Library folder and is using 56.4 GB of space (about 30% of my total disk usage; drilling down further shows that 43.6 GB of that is attachments):

In this case, deleting the files directly in Finder is not the best approach (that is one reason the ~/Library folder requires the extra step of holding down the option key to access it from the Go menu). Rather, I would need to go into Outlook and use that app’s search/sort tools to identify the emails with large attachments and delete the emails, or just the attachments if desired. 

The app(s) using large amounts of storage space in Other, and the best way to free up that storage space, will depend on the app(s) installed. Hopefully the above information enables you find the files on your drive that are taking up the most space. You can then free up needed space by deleting those files or moving them to an external drive.

There is a forum devoted entirely to Outlook at

https://answers.microsoft.com/en-us/outlook_com/forum/outlk_Mac?sort=LastReplyDate&dir=Desc&tab=All&status=all&mod=&modAge=&advFil=&postedAfter=&postedBefore=&threadType=all&isFilterExpanded=false&page=1

User wrote " So in light of this big update to do with Apple - I am trying to upgrade a lot of Apple Mac's to the latest firmware, however, I am met with no space all the time. "

A - The latest Firmware or EFI Boot ROM ? Apple Includes this in Monterey for Qualifying Apple Computer that requires it.

Apple has ceased offering Standalone Firmware updates for some time now and generally includes it in various versions of macOS

Rebuild the Spotlight index on your Mac

What is “Other” storage on a Mac, and how can I clean it out?

Free up storage space on your Mac

GrandPerspective 

How to delete Time Machine snapshots on your Mac

See used and available storage space on your Mac

Locate backups of your iPhone, iPad, and iPod touch

Notation - If the user is using a cloning software like Carbon Copy Cloner - suggest tweaking the Safety Net Feature in this software. It may be making addition Snap Shots that are not being Cloned to the Eternal Drive. If this should be the case, these Snap Shot could be using additional space on the drive 

The final word from Apple on Managing the " Other/ System Data “ Category

Other / System Data: Contains files that don’t fall into the categories listed here. This category primarily includes files and data used by the system, such as log files, caches, VM files, and other runtime system resources. Also included are temporary files, fonts, app support files, and plug-ins. You can't manage the contents of this category. The contents are managed by macOS, and the category varies in size depending on the current state of your Mac.

The space your Outlook data takes up depends on what you have in it.

Starting with Office 2016, MS finally stopped using their old Mac database, which no longer required the separate tool to optimize it. When you delete items from the Deleted folder, they're gone. You don't need to do anything else.

So, that means you have a lot of live emails in your various folders (Inbox, Sent, Deleted, etc.) that probably have large attachments in them. Such as photos and videos. They only way to remove them - properly - to claim back that space is to go through all of your emails you don't need, put them in the trash, and then empty the trash.

That is the mail store for Microsoft Outlook.