📧 Outlook Mailbox Cleanup Guide

This guide helps you free up space in your Outlook mailbox by removing unnecessary content and organizing your email.

📌 Frequently Asked Questions

1. How can I see what is using the most space in Outlook?

You can view your mailbox size using the Mailbox Cleanup tool.

  1. Open Outlook
  2. Select File
  3. Select Info
  4. Select Tools
  5. Select Mailbox Cleanup
  6. Select View Mailbox Size

📊 You will see your total mailbox size and each folder’s size.


2. How do I find and delete large emails?

Large emails take up the most space.

Steps:

  1. Go to the Search bar
  2. Type size:>10MB
  3. Or try size:>5MB
  4. Sort by Size
  5. Delete emails you do not need
  6. Empty Deleted Items
  7. Select Folder > Recover Deleted Items to remove permanently

⚠️ Important: Deleting emails does not free space until Deleted Items is emptied.


3. How do I remove attachments but keep the email?

This keeps important emails while freeing space.

  1. Open the email
  2. Right-click the attachment
  3. Select Save As
  4. Choose a location (computer or cloud)
  5. Select the attachment again
  6. Select Remove Attachment
  7. Save the email

💡 Tip: Save attachments to OneDrive or SharePoint for easy access.


4. Which folders do people forget to clean out?

These folders often become large:

  • 🗑️ Deleted Items
  • 🚫 Junk Email
  • 📤 Sent Items
  • 💬 Conversation History

📌 Check these folders regularly and delete items you do not need.


5. How can I sort my email by size?
  1. Open your Inbox
  2. Select the Size column

If you do not see it:

  1. Select View
  2. Select View Settings
  3. Select Sort
  4. Select Size
  5. Select OK

🔍 Sorting helps you quickly find large emails.


6. How do I archive older emails?
  1. Select File
  2. Select Info
  3. Select Tools
  4. Select Clean Up Old Items
  5. Choose a date
  6. Save the archive file

📦 Archiving keeps your mailbox small without deleting emails.


7. What does “Compact Now” do?

Compacting reduces file size after deletions.

  1. Select File
  2. Select Account Settings
  3. Select Account Settings again
  4. Select Data Files
  5. Select your file
  6. Select Settings
  7. Select Compact Now

⚙️ Use this after large cleanups.


8. How do I clean up long email conversations?
  1. Select Home
  2. Select Clean Up
  3. Select Clean Up Folder

🧹 This removes duplicate messages.


9. What if my Microsoft 365 mailbox is still full?

You may have an Online Archive mailbox.

  1. Select File
  2. Select Info
  3. Look for Online Archive
  4. Move older emails there

📁 This helps keep your main mailbox within limits.

✅ Best Practices

  • 🗑️ Delete unnecessary emails regularly
  • 📅 Empty Deleted Items weekly
  • 📎 Save large attachments outside Outlook
  • 📦 Archive emails older than 6–12 months
  • ⚙️ Use cleanup tools monthly

💡 Tip: Regular cleanup prevents mailbox full warnings and improves Outlook performance.