My Microsoft Outlook mailbox is almost full — it’s at 93% capacity.

Question

Hello,

My Microsoft Outlook mailbox is almost full — it’s at 93% capacity.

could you please help to move lots of my inbox files to the archieve file？

Thank you!

---

Moderator note: Change tag from: Outlook | Windows | Classic Outlook for Windows | For business

Answer 1

Dear @Fan Feng, 

Thank you for reaching out and sharing your concern. 

The Archive button in Outlook only moves items into the Archive folder within the same mailbox, which helps with organization but does not reduce the mailbox size on the server. To free up space effectively, you will need to move emails either to an Online Archive for Microsoft 365 enterprise or to a local data file (pst), depending on the type of account you are using. 

Since you didn't specify whether your account is personal, work, or school, I have outlined the options below so you can choose what best fits your environment: 

Option 1: Move emails to an Online Archive (Recommended if your organization provides this feature) 

Notes:  

• The Online Archive is available for Microsoft 365 Exchange work or school accounts and offers extra space to manage large mailboxes.  
• Personal accounts and POP or IMAP accounts do not support this feature, so these account types can organize mail using local pst files or other archiving methods instead. 

Open Outlook and look at your folder list. If you see a folder named “Online Archive – ”, the feature is already enabled. 

Select any emails or folders you want to move. 

On the toolbar, choose Home > Move > Other Folder. 

Select the Online Archive as the destination. 

Once moved, these items no longer count toward your primary mailbox quota. 

If the Online Archive is not visible, your Microsoft 365 administrator may need to enable it for you. 

This article provides further guidance on the topic: Manage email storage with In-Place/Online Archive mailboxes - Microsoft Support 

Option 2: Move emails to a local pst file (Works for any account type and reduces server space) 

Notes:   

• A pst file is stored locally on your computer. Its contents do not sync across devices.  
• It is not included in server‑side backups. Please keep it in a secure folder or backup location.  

In Outlook, select New Items > More Items > Outlook Data File. 

Choose a name and a location that you can easily remember. 

To archive older items in bulk, go to File > Info > Tools > Clean up old items. 

Select the Inbox and choose a cutoff date such as emails older than six months. 

Browse to the pst file you created and confirm. 

• Optional automatic archiving: If you prefer ongoing automatic cleanup, go to File > Options > Advanced > AutoArchive Settings. You can choose how often the archive runs and where items should be stored. If you would like to explore automatic archiving in more detail, you can review the following resource: AutoArchive settings explained - Microsoft Support 

As community moderators, we kindly ask for your understanding that our access to internal development details is limited. Our primary role is to guide users toward the appropriate resources and support channels. While we may not have visibility into performing deeper backend analysis, we’ll continue doing our best to support you within the scope of our responsibilities.  

I hope this information is helpful. If you have any questions or need further support, please don’t hesitate to reach out at any time. 

Thank you for your patience and understanding. 

---

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have any extra questions about this answer, please click "Comment".            

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. 

Answer 2

To free space and move items from the Inbox to archive in Outlook for Windows (classic), use a combination of archiving and cleanup tools.

1. Move older items to an Outlook Data File (.pst)

• In Outlook, select the File tab.
• Choose Tools > Mailbox Cleanup.
• Use Find items older than to identify old messages to move.
• Create or choose an Outlook Data File (.pst) and move those items into it (drag/drop or use Move commands). This file is stored locally and does not count against server mailbox quota.
• You can also configure automatic archiving so Outlook regularly moves older items to a .pst. See Archive older items automatically and Archive items manually.

2. Use Mailbox Cleanup to reduce size

• In File > Tools > Mailbox Cleanup:
  • Select View Mailbox Size to see which folders are largest.
  • Use View Deleted Items Size and Empty Deleted Items folder to clear that folder.
  • Use View Conflicts Size and Empty Conflicts if present.

3. Delete or move large messages

• In the main Outlook window, click in the Search box and type: messagesize:>5 mb to find messages larger than 5 MB.
• Delete unneeded large messages or move them to a .pst archive file.

4. Keep mailbox lean going forward

• Regularly archive older items to a .pst file.
• Empty Deleted Items and Junk Email folders frequently.
• Save large attachments outside the mailbox (for example, to OneDrive or local folders) and then delete the original messages or attachments from the mailbox.

If the Archive feature is enabled but the mailbox still grows, ensure items are actually being moved either manually or via configured automatic archive/retention policies.

---

References:

• Manage my mailbox size in Outlook
• Mailbox storage limits in Outlook
• Reduce the size of your mailbox and Outlook Data Files (.pst and .ost)
• Your mailbox reaches its quota even if the Archive feature is enabled