Your mailbox is almost full Outlook 365 message

Do you keep getting the Your mailbox is almost full emails from the Outlook team? Some Outlook users have reported that they keep receiving emails that say:

Your mailbox is almost full.
Please reduce your mailbox size. Delete any items that you don’t need from your mailbox and empty your Deleted Items folder.

The warning message clearly indicates that you are running out of storage space on Outlook.

How do I free up mailbox space in Outlook 365?

There are different methods to make free space in your mailbox in Outlook. You can delete old emails, clear large-size emails, clear duplicate emails, delete attachments, and permanently delete trashed items. This post will show you how to clean up, compact and reduce mailbox size in Outlook.

Note: Spammers and hackers can send such messages. So, do check whether the email is sent by the official Office/Outlook team or not. Also, avoid clicking any link present inside the mail as those links can be malicious and expose your account to potential threats.

Your mailbox is almost full Outlook 365 message

If you keep receiving a warning message from the Outlook team saying Your mailbox is almost full, here are the methods to free up some storage space on Outlook and fix this issue:

1. Clean up Outlook inbox using the Mailbox Cleanup tool.
2. Delete Duplicate emails.
3. Auto-empty Deleted Items folder on Outlook restart.
4. Manually archive your old emails.
5. Move attachments to OneDrive.
6. Turn off Cached Exchange Mode.
7. Compress the Outlook PST file.
8. Increase Outlook data file limit.
9. Upgrade your Outlook.com account.

1] Clean up Outlook inbox using the Mailbox Cleanup tool

Outlook provides a built-in Mailbox Cleanup tool that you can use to make some storage space in your inbox. Here’s how you can run it:

• First, open Outlook and go to the File menu.
• Now, from the Info tab, select the Tools drop-down menu button.
• Next, click on the Mailbox Cleanup tool.

Once you have opened the Mailbox Cleanup tool, you can perform the following actions to clean up junk and free up Outlook storage space:

A) Clear your Deleted Items folder

You can make some space by clearing your Deleted Items folder in Outlook. This folder contains the items, including emails and conversations you previously deleted. Click on the Empty button next to the Emptying the deleted items folder permanently deletes those items option. If you want to check the size of deleted items, you can click on the View Deleted Items Size button.

B) Auto-archive old emails

You can set up Auto-archive for your old emails to make some space in your primary inbox on Outlook. For that, click on the AutoArchive button in the Mailbox Cleanup dialog window.

C) Find large emails and delete them

The next thing you can do using the Mailbox Cleanup tool is to look for emails larger than the specified size and delete them if not needed. This will make some space in your Outlook inbox. You can also find emails older than a particular number of days and remove them.

You can enter the number of days in the Find items older than box and click on the Find button. Or, you can enter a specific size in the Find items larger than box and hit the Find button. It will then look and find the items. You can select and delete the items you don’t require.

TIP: Delete all emails before or after a date in Outlook.

Another method is to delete large emails in Outlook without using the Mailbox Cleanup tool. Here are the steps to do that:

Open Outlook and go to the Home tab.

Now, click on the Search Folders from the left-side pane. Next, select the New Search Folder option.

After that, under the Organizing Mail section, select the Large mail option.

Then, beneath the Customize Search Folder option press the Choose button.

Now, enter the mail size inside the Show mail greater than box and press the OK button.

It will then show you all the emails that are above the specified size limit. You can then choose to delete the emails if you don’t need them.

2] Delete Duplicate emails

Duplicate items can also occupy a significant amount of space in your inbox on Outlook. To delete the duplicate emails, follow the below steps:

• Go to the Home tab in Outlook and make sure you have selected the Inbox folder.
• Click on the Delete drop-down button.
• Choose the Clean Up Folder option.
• Finally, press the Clean Up Folder button in the confirmation prompt.

Outlook will now clear all the redundant and duplicate conversations.

3] Auto-empty Deleted Items folder on Outlook restart

If you want to automatically clear the Deleted Items folder in Outlook whenever you close the app, you can do that by tweaking its settings. It will ensure that the trash items are permanently deleted and will help you optimize storage space in Outlook.

Here are the steps to permanently clear Outlook’s deleted items after every restart:

• First, click on the File menu in Outlook.
• Now, select Options and move to the Advanced tab in the Outlook Options window.
• Next, under the Outlook start and exit option, tick the Empty Deleted Items folders when exiting Outlook box.
• Lastly, press the OK button.

See: Fix Outlook error 0x8004060c during Send/Receive operation.

4] Manually archive your old emails

You can also manually archive your old emails as follows:

• First, go to the File menu and move to the Info > Tools > Clean Up Old Items option.
• Now, select the folders and sub-folders that you want to archive.
• Next, enter the date to archive items older than that specific date.
• After that, select the archive file and press the OK button to start the email archiving process.

5] Move attachments to OneDrive

The next thing you can do to free up storage space on Outlook is to save your attachments to your OneDrive account. Here are the steps to do that:

• First, click on the Filter option present at the top of our email list.
• Now, select the Sort by > Size option.
  Note: If the emails are sorted in ascending order, tap on Filter > Sort by > Size again.
• After that, choose the email that contains attachments.
• Next, click on the Save to OneDrive present under the attachment.
• You can now delete the original email.
• Repeat the above process for all other emails to move attachments to OneDrive.

Read: How to optimize and speed up Microsoft Outlook?

6] Turn off Cached Exchange Mode

Disable the Cached Exchange Mode and see if the warning message is stopped. This feature, when enabled, saves a local copy of the mailbox for quick access to data. However, it might be consuming a good amount of storage space. To disable it:

• Open Outlook and navigate to the File menu.
• Now, from the Info tab, select the Account Settings > Account Settings option.
• After that, choose your active account and click the Change button.
• In the appeared window, select the  Use Cached Exchange Mode to download email to an Outlook data file checkbox.
• Once done, click on the Done button and restart the Outlook app. Check if you have stopped receiving the “Your Mailbox is almost full” message.

See: The message cannot be sent right now Outlook error.

7] Compress the Outlook PST file

The next thing you can do to fix this issue is to compress the Outlook PST file and see if it works. Here are the steps to do that:

• First, open Outlook and click on the File menu.
• Now, move to the Account Settings option and select the Account Settings option.
• Next, go to the Data Files tab and choose the Outlook data file you want to compress.
• After that, press the Settings button and click the Compact Now button.
• Once the PST file is compressed, check if the problem is fixed.

Read: Outlook Quota Exceeded, The account is above quota limits.

9] Increase Outlook data file limit

You can also increase the size limit for PST files using Registry Editor and check if it helps fix the issue.

10] Upgrade your Outlook.com account

You get a free 15 GB of email storage for your Outlook.com account. If you want more storage space, you can upgrade your Outlook account. It will give you a 50 GB mailbox per person, advanced email security, and an ad-free inbox.

I hope this helps!

Read: Cannot expand the folder; Not enough free memory Outlook error.

Can you increase mailbox size in Office 365 more than 100GB?

No, you can’t increase the mailbox size beyond 100GB in Office 365. The maximum limitation on a mailbox folder is 100GB for all Office subscription plans. And the archive mailboxes have a storage limit of 50GB. However, high-end subscription plans like Microsoft 365 Enterprise E3/E5, Office 365 Enterprise E1, etc., can have a storage limit of 1.5 TB for archives.