It takes up space from Macbook's local disk after exporting Outlook for Mac Archive to an external disk

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It takes up space from Macbook's local disk after exporting Outlook for Mac Archive to an external disk

Trung Nguyen 0

After I finished exporting Outlook for Mac Archive (.olm file about 720 GB) to an external disk, I realize that it also takes up space (about 100 GB) from Macbook's local disk. Then I try to understand what is happening? And I know that Outlook creates a temporary cache or copies the data locally to the Macbook before or while transferring it to the external disk for this Export funtion on Legacy Outlook. I currently use Outlook LTSC Standard for Mac 2024.

I need to free up that space (about 100 GB) of local disk, and I tried to find those files in ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles, but I haven't seen it.

Could anyone help with below questions?

I wonder that if this export (Outlook for Mac Archive) is included both server emails & local emails stored "On My Computer" or not?
How to remove those temporary files to free up space of local disk? Is it safe to remove it without affecting current emails? And where it is on Macbook?

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Answer 1

Gabriel-N 16,475 Microsoft External Staff Moderator

Hi Trung Nguyen

First, I recommend reviewing the AI‑generated response on your post, as it already includes some helpful insights that align closely with the general behavior of Outlook for Mac in this scenario.

In addition, I’d like to clarify a few points. In Legacy Outlook for Mac, exporting to an .olm archive may include both server‑based items (such as Exchange or IMAP mailbox data) and local data stored under On My Computer (mail, calendar, contacts, tasks, notes), depending on what folders were selected during the export process. So it would be a “yes” for your first question. However, to further confirm, you might also want to log in to your mailbox on the web to check whether your server‑based mailbox content is still available there.

About the local disk space usage after export, Outlook for Mac is a locally cached email client, which means it stores mailbox content locally within a profile located in your home folder at: ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles

If you are unable to locate the expected files and have already successfully backed up the .olm file to an external disk, you may consider verifying that the .olm file is valid and confirming that your mailbox data is still available on the server (for Exchange / Microsoft 365 accounts) before attempting to remove or reorganize any locally stored content such as items under On My Computer.

Please note that items stored under On My Computer are local‑only and are not restored from the server if removed from the Outlook profile.

However, I would like to clarify whether your intention is to remove locally stored mail to free up disk space, or to remove items from the server as well. If your intention is to remove emails from the server, this action would need to be performed directly on your mail server (for example, via Outlook on the web). Since Legacy Outlook for Mac operates as a locally cached client, it will download mailbox data from the server to your device after sign‑in, which means the local storage used on your Mac may continue to increase as long as those items remain available on the server. In simple terms, your emails are stored on the mail server, and when you sign in to Outlook, a copy of those emails is also saved on your Mac for offline access and performance.

So the same email may exist:

On the mail server
On your Mac after syncing
And under On My Computer if you have exported or moved it locally

I hope this helps clarify the situation. If you have any further questions, please feel free to reach out.

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Trung Nguyen 0 Reputation points

2026-04-13T14:25:09.7466667+00:00

Hi @Gabriel-N

Thanks for your reply & comments.

My server email is still available there. When I did make export, there were all items like this, and I selected all items to do it.

As for server-based email & locally email stored under "On My Computer", I know how to remove it on email server and under "On My Computer" of Outlook for Mac.

So your reply to my first question is ok. However, the answer to the second question is not to the point. As my understanding, when export data to an external disk, it won't take space on local disk (like Windows), however, this function on Mac is different.

In my case, Outlook for Mac Archive.olm file is about 720 GB on my external disk, however, this export job of Outlook also tooks up about 100 GB from my Mac's local disk space. Therefore, I would like to identify where is the files/folders for this space (about 100 GB) in order to remove it? And is it safe to remove it without affecting my current emails? How to remove it?

Hope you can help me with this case. Thank you!
Gabriel-N 16,475 Reputation points Microsoft External Staff Moderator

2026-04-14T08:29:56.93+00:00

Hi Trung Nguyen

Sorry for the confusion earlier and the late reply.

About your second question, what I meant regarding the server is that you should double-check whether your mailbox on the server is actually around 100 GB. If it is, then Outlook on your Mac may have synced and downloaded all that data locally, which could explain the 100 GB usage.

If that’s not the case, and you’ve already exported everything important to the .olm file and confirmed it’s complete, I recommend deleting or renaming the “Main Profile” folder inside: ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles
Then, reopen Outlook and sign in again, it will create a fresh profile. This can help determine whether the 100 GB was just temporary cache or still being used.

Just make sure you’ve backed up everything important before doing this.

Let me know how it goes.
Trung Nguyen 0 Reputation points

2026-04-15T03:21:30.8466667+00:00

Hi @Gabriel-N

My server mailbox is max.50 GB only, so when this mailbox is full, I will need to backup it into my computer.

I just check server mailbox, it's about 32 GB. So that's not the case here.

All my emails have been exported completely to Outlook for Mac Archive.olm file, it's 720 GB+. There are 2 folders at ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles, one is Main Profile (23.5 MB), and the other folder is Profile 1 (872.29 GB). The folder "Main Profile" should be the old one, and the folder "Profile 1" should be the current mail that I'm using (it should be created by one IT several years ago).

So, in this case, I can remove folder "Main Profile" safely without affecting current email, is it right?

And If I rename folder "Profile 1", then re-open Outlook, current email in "Profile 1" can be shown under "On My Computer" or not? Or if renaming folder "Profile 1", then re-open Outlook, it will automatically create a new profile (without any current email inside under "On My Computer")? If yes with no current email under a new profile, and I need to use current email for working, I have to import "Outlook for Mac Archive.olm file" back in Outlook?

Thanks for your further advice & instruction.
Gabriel-N 16,475 Reputation points Microsoft External Staff Moderator

2026-04-15T14:03:42.64+00:00

Hello Trung Nguyen

You can safely delete the "Main Profile" folder without affecting your current emails because you've already backed it up to an external drive.

As for "Profile 1", I recommend that you also back it up to an external drive by exporting it to an .olm file, just like you did with "Main Profile". Copying the entire folder manually is not the method recommended by Microsoft, so exporting is the safer and more reliable approach.

In short, if you want to rebuild your Outlook profile, you should always back up everything first (especially "On My Computer" data), then proceed with the rebuild, and finally import the backup to restore your data properly.

Hope this clarify the situation.
Gabriel-N 16,475 Reputation points Microsoft External Staff Moderator

2026-04-17T07:13:30.3533333+00:00

Hello Trung Nguyen

If you still have further concerns, please feel free to let me know.
Trung Nguyen 0 Reputation points

2026-04-21T04:01:29.4333333+00:00

Hi @Gabriel-N

Thanks for your message.

Actually, I really concern about freeing space from disk regarding to Outlook on Mac as it takes much space from my Mac. Now, I still can't identify those 100GB on my Mac to remove it in order to free up my disk's space.

I found one thing is strange on Outlook app. I see that the size of Outlook is 3.29 GB and size of all Applications is 25.8 GB during Outlook opening, but later, Outlook size is up to 161.37 GB, and total Applications size is 235.79 GB (as per att'd 2 above pictures). I have a look at this several times when I open my Macbook & Outlook & it's still like that. Could you pls advise me how it is? This increased size of Outlook is occupying my disk's space?
Gabriel-N 16,475 Reputation points Microsoft External Staff Moderator

2026-04-21T09:15:44.4266667+00:00

Hello Trung Nguyen , please check your private message for better assistance and to avoid unnecessary back-and-forth. Thank you.
Gabriel-N 16,475 Reputation points Microsoft External Staff Moderator

2026-04-22T10:07:52.3533333+00:00

Hello Trung Nguyen , could you please check private messages when you get a chance? I’ll need a few more details to better assist you.

Answer 2

Scope of what gets exported

In Legacy Outlook for Mac, exporting to an .olm archive includes:

Server‑based items (for example, Exchange/IMAP mailboxes) that are selected in the export dialog.
Local data stored under On My Computer (mail, calendar, contacts, tasks, notes) if those folders are selected during export.

After import, all archived content appears under On My Computer in Outlook for Mac.

“In Outlook, email messages, contacts, calendar items, tasks, and notes can be exported to archive files. You can import these files (.pst in Outlook for Windows and .olm in Outlook for Mac) into Outlook for Mac. Once imported, the archived content can be found in the On My Computer section…”

So, if On My Computer folders were included in the export options, both server and local items are in the .olm file.

About local cache and temporary space

Outlook for Mac is a locally cached client. It keeps a full local cache of mailbox data in the profile/identity location and is designed to work this way:

“Outlook 2016 for Mac caches your mail items in a profile in your home folder at the following location: ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles

Like Microsoft Entourage for Mac 2008, Outlook 2016 for Mac and Outlook for Mac 2011 are intended to be purely locally cached mail clients.”

The extra 100 GB seen after export is almost certainly:

The normal Outlook profile cache (which always resides locally), plus
Any additional working space/macOS temporary files used during the export.

Outlook does not support moving the profile/identity to external or network storage:

“We do not recommend that you change the default location of your Profile folder… to an external hard disk or to a network. Additionally, using a mail identity or profile that is located on an external hard disk or on a network is not supported…”

How to safely free local disk space

From the provided information, there is no documented, supported method to selectively delete only the temporary export files. What is documented and supported is:

Outlook must keep a local cache in the profile folder.
That profile location must remain on the local disk.

To reduce local disk usage in a supported way, the options documented are:

Use an online archive mailbox (if using Exchange/Exchange Online and if the admin has enabled it). Older mail can be moved to the online archive so it no longer resides in the primary mailbox cache:

“An online archive—also called an archive mailbox—is a place where you can store old email messages so they don't take up space in your primary mailbox. Your IT or Microsoft 365 admin creates the archive mailbox for you.”

This reduces the size of the primary mailbox that Outlook caches locally.
Export items to an .olm file and then delete or move items from Outlook (for example, from On My Computer or from server folders) so they are no longer cached. The export/import behavior is:

“In Outlook, email messages, contacts, calendar items, tasks, and notes can be exported to archive files. You can import these files (.pst in Outlook for Windows and .olm in Outlook for Mac) into Outlook for Mac. Once imported, the archived content can be found in the On My Computer section…”

After confirming the .olm on the external disk is valid and backed up, items can be removed from Outlook to shrink the profile. Outlook will then reduce its local cache as those items are no longer present.

There is no supported guidance in the provided material for manually locating and deleting specific temporary export files beyond the standard profile and cache locations, and manually deleting unknown files risks corrupting the Outlook profile.

Summary:

The .olm export can include both server and On My Computer items, depending on what was selected.
Outlook for Mac always maintains a local cache in the profile folder; this cannot be moved off the local disk in a supported way.
To free space in a supported manner, use online archive mailboxes (for Exchange/Exchange Online) and/or export to .olm and then delete items from Outlook so the profile cache shrinks, rather than manually deleting undocumented temporary files.

References:

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It takes up space from Macbook's local disk after exporting Outlook for Mac Archive to an external disk

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