Summary

This guide helps you troubleshoot and resolve: Office 365 Mailbox Almost Full How To Fix Australia. Follow the steps below to fix the issue.

Common Causes

Office 365 Mailbox Almost Full: How to Fix

Microsoft 365 mailboxes are assigned a specific storage quota based on your subscription plan. When a mailbox reaches its limit, it will stop accepting incoming messages, and anyone attempting to email you will receive a Non-Delivery Report (NDR). You may also find that you are unable to send new emails. This guide explains how to check your current mailbox usage, identify large items consuming storage, and reclaim space to restore normal email delivery.

Quick Fix Steps

1. Check your current mailbox storage usage via Outlook on the web.
2. Empty the Deleted Items folder to remove items waiting for permanent deletion.
3. Empty the Junk Email folder to clear out spam and marketing messages.
4. Search for and delete emails with large attachments.
5. Archive older emails to an online archive or local data file.

Detailed Instructions

Check Mailbox Storage Usage

1. Open a web browser and sign in to Outlook on the web using your Microsoft 365 email address and password.
2. Click the Settings (gear) icon in the top-right corner.
3. Select Mail from the left-hand menu, then choose Storage.
4. Review the storage bar to see how much of your quota is currently in use.

Note: If your mailbox is at or near 100%, you will be unable to send or receive new email until space is freed up.

Empty Deleted Items and Junk Email

1. In Outlook on the web, right-click the Deleted Items folder in the folder pane.
2. Select Empty folder and confirm the action when prompted.
3. Right-click the Junk Email folder.
4. Select Empty folder and confirm.

Find and Delete Large Emails

1. In Outlook on the web, click into the search bar at the top of the page.
2. Type size:>5MB and press Enter to find emails larger than 5 megabytes.
3. Review the results and select any emails you no longer need.
4. Click the Delete icon or press Delete on your keyboard.
5. Remember to empty the Deleted Items folder afterwards to permanently reclaim the space.

Tip: You can adjust the search filter to size:>10MB or size:>20MB to target the largest messages first.

Archive Older Emails

1. Open the Outlook desktop application on your computer.
2. Select the emails or folders you want to move out of your primary mailbox.
3. Click File, then select Info.
4. Choose Tools and click Clean Up Old Items.
5. Select Archive this folder and all subfolders, choose your folder, and set a date for items to be archived.
6. Click OK to move older items to an archive data file.

Warning: Archiving to a local .pst file removes items from the server mailbox. Ensure these files are included in your organisation's regular backup routine.

Troubleshooting

Mailbox Still Full After Deleting Items

Deleted items are not permanently removed until the Deleted Items folder is emptied. If you have deleted messages but your usage has not decreased, empty the Deleted Items folder and check the storage again. Items in the Recoverable Items folder may also count toward your quota; these are typically cleared automatically after the retention period expires.

Receiving Non-Delivery Reports (NDRs)

If senders are receiving bounce-back messages, your mailbox is likely over its storage limit. Free up space using the steps above, then ask the sender to resend the message. If you continue to experience email delivery issues, you may need to review your mailbox plan or check for other delivery problems.

Storage Quota Not Updating

Storage usage in Microsoft 365 can take some time to update after large deletions. Wait 15 to 30 minutes and refresh Outlook on the web to see the updated quota. If the usage does not change after an hour, Open a Ticket for assistance.

Preventing Future Storage Issues

• Regularly review and delete emails with large attachments.
• Save important attachments to OneDrive or a shared drive and remove them from the email.
• Use archive policies to automatically move older emails out of your primary mailbox.
• Monitor your storage usage periodically through Outlook on the web.
• Consider upgrading your Microsoft 365 plan if your organisation consistently exceeds its mailbox quota.

If you host with us, you don't need to do this yourself — just Open a Ticket and our Brisbane team will get it sorted.

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