How To Free Up Space On Outlook – Clearing Outlook Mailbox Space

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Managing your Outlook mailbox size starts with identifying and removing large or unnecessary items. If you’ve ever been stuck with a full inbox and can’t send or recieve emails, you know the frustration. This guide shows you exactly how to free up space on outlook using built-in tools and a few smart tricks.

Outlook stores emails, attachments, calendar items, and tasks. Over time, these pile up. A bloated mailbox slows down performance and may trigger storage limits. Let’s fix that step by step.

Why Your Outlook Mailbox Gets Full

Your mailbox fills up for several reasons. Large attachments are the biggest culprit. Emails with photos, PDFs, or presentations eat up space fast. Also, deleted items often stay in the “Deleted Items” folder instead of being removed permanently. Junk mail, old conversations, and calendar clutter add to the problem.

If you use Microsoft 365 or Exchange, your mailbox has a storage limit. For most users, that’s 50 GB. Once you hit 90% of that, Outlook starts warning you. For free Outlook.com accounts, the limit is 15 GB. Knowing these limits helps you plan your cleanup.

How To Free Up Space On Outlook

Now let’s get into the main methods. These steps work for Outlook 2016, 2019, 2021, and Microsoft 365. They also apply to Outlook.com and the Outlook app for Mac. Follow each section carefully.

Use The Mailbox Cleanup Tool

Outlook has a built-in tool that makes cleanup easy. Here’s how to access it:

  1. Open Outlook and click the File tab.
  2. Select Tools from the menu.
  3. Click Mailbox Cleanup.

This tool shows you your total mailbox size and breaks it down by folder. You can see which folders are the largest. From here, you can:

  • View the size of each folder.
  • Find items older than a certain date.
  • Find items larger than a specific size (like 5 MB).
  • Empty the Deleted Items folder.
  • Archive old items.

Start by clicking Find items larger than and set it to 5 MB. Outlook will list all emails with attachments over that size. Delete or move them to a local folder.

Empty The Deleted Items Folder

This is the quickest win. Many people forget that deleted emails stay in the Deleted Items folder until you empty it. To do this:

  1. Right-click the Deleted Items folder in the left pane.
  2. Select Empty Folder.
  3. Confirm when prompted.

If you use Outlook.com, go to the Deleted folder and click Empty folder at the top. This frees up space instantly. But be careful—once emptied, you can’t recover those emails unless you have a backup.

Clear The Junk Email Folder

Junk mail also takes up space. Outlook automatically moves spam to the Junk Email folder. To clear it:

  1. Go to the Junk Email folder.
  2. Select all items (press Ctrl+A).
  3. Press Delete or right-click and choose Delete.

After deleting, empty the Deleted Items folder again. This two-step process ensures junk mail is gone for good.

Archive Old Emails

Archiving moves old emails to a separate data file (.pst) without deleting them. This keeps your mailbox small while preserving your history. To set up auto-archive:

  1. Click File > Options > Advanced.
  2. Under AutoArchive, click AutoArchive Settings.
  3. Check Run AutoArchive every and set a frequency (like 14 days).
  4. Choose to archive items older than 6 months or 1 year.
  5. Specify a location for the archive file.

You can also manually archive. Go to File > Tools > Clean Up Old Items. Select a date and let Outlook move everything older to an archive folder.

Delete Large Attachments

Attachments are space hogs. To find and remove them:

  1. Use the Mailbox Cleanup tool as described earlier.
  2. Click Find items larger than and set a size like 2 MB.
  3. Review the list. Delete emails with attachments you don’t need.

Alternatively, you can save attachments to your computer or cloud storage, then delete the email. To save an attachment, open the email, right-click the attachment, and choose Save As. After saving, delete the email.

Compact Your Outlook Data File

Even after deleting items, your Outlook data file (.ost or .pst) may not shrink. Compacting it reclaims unused space. Here’s how:

  1. Close Outlook.
  2. Open Control Panel and go to Mail (search for “Mail” if you can’t find it).
  3. Click Data Files.
  4. Select your mailbox file and click Settings.
  5. Click Compact Now.

This process can take a few minutes. Don’t interrupt it. After compacting, you’ll see a smaller file size.

Use Outlook Web App (OWA) For Bulk Deletion

If you use Exchange or Office 365, the web version of Outlook has powerful search features. You can delete thousands of emails at once. For example:

  • Search for “hasattachment:yes” to find all emails with attachments.
  • Search for “size:>5MB” to find large emails.
  • Search for “received:<01/01/2023" to find old emails.

After the search, select all results (press Ctrl+A) and delete them. This is much faster than doing it one by one.

Turn Off Conversation History

Skype and Teams conversations can clutter your mailbox. To turn off saving conversation history:

  1. In Outlook, go to File > Options > Mail.
  2. Under Save messages, uncheck Save copies of messages in the Sent Items folder (if you don’t need them).
  3. Also uncheck Save Skype for Business conversations in the Conversation History folder.

This stops future clutter. For existing conversation history, delete the folder contents manually.

Reduce Calendar And Task Clutter

Old calendar items and tasks also take space. To clean them:

  • Go to your Calendar folder. Right-click it and choose Properties > AutoArchive. Set it to archive items older than 6 months.
  • For Tasks, do the same. Archive or delete completed tasks from years ago.

You can also manually delete old calendar entries by switching to List view and sorting by date.

Use The “Clean Up” Feature

Outlook’s Clean Up tool removes redundant messages from long email threads. It keeps the latest reply and deletes the rest. To use it:

  1. Select a folder (like Inbox).
  2. Go to the Home tab.
  3. Click Clean Up > Clean Up Folder.

This can remove hundreds of duplicate emails quickly. Check the preview before confirming.

Move Emails To Local Folders

If you have a lot of important emails, move them to a local .pst file on your computer. This takes them out of your online mailbox. To create a local folder:

  1. Right-click your mailbox name in the left pane.
  2. Select New Folder.
  3. Name it something like “Archive 2023.”
  4. Drag and drop emails from your Inbox into this folder.

Note: Local folders are not backed up in the cloud. Make sure to back up your .pst file regularly.

Check For Rules And Add-Ins

Sometimes Outlook runs slowly because of too many rules or add-ins. Rules that automatically move emails can cause duplicates. To review rules:

  1. Go to File > Manage Rules & Alerts.
  2. Disable or delete rules you don’t need.

For add-ins, go to File > Options > Add-ins. Disable any that are not essential. This can improve performance and reduce mailbox bloat.

Use The “Search Folders” Feature

Search Folders are virtual folders that show emails matching criteria. You can create a Search Folder for large emails or old emails. This helps you find and delete them faster. To create one:

  1. Right-click Search Folders in the left pane.
  2. Select New Search Folder.
  3. Choose Mail with specific words or Large mail.
  4. Set the size criteria (like over 5 MB).

Then delete the emails from that Search Folder.

Consider Upgrading Your Plan

If you’ve cleaned everything and still need more space, consider upgrading your Microsoft 365 subscription. Higher tiers offer up to 100 GB or unlimited storage. For personal use, Microsoft 365 Basic gives you 100 GB of mailbox space. For business, plans go up to 1.5 TB per user.

But before upgrading, try all the methods above. Most users can free up 10-20 GB easily.

Frequently Asked Questions

How Often Should I Clean My Outlook Mailbox?

Ideally, do a quick cleanup every month. Use the Mailbox Cleanup tool to delete large items. Set up auto-archive to run every 14 days. This prevents the mailbox from getting full again.

Will Deleting Emails From Outlook Delete Them From The Server?

It depends on your account type. For Exchange and Office 365, deleting from Outlook also deletes from the server. For IMAP accounts, it may or may not. Check your account settings. For POP3, emails are usually downloaded and then removed from the server.

Can I Recover Deleted Emails After Emptying The Deleted Items Folder?

In most cases, no. But if you use Exchange or Office 365, you might have a “Recoverable Items” folder. Go to the Deleted Items folder and click Recover items recently removed from this folder. This only works for items deleted within the last 30 days.

Does Archiving Emails Free Up Space On Outlook?

Yes, archiving moves emails to a local .pst file, which is not counted toward your mailbox quota. Your online mailbox becomes smaller. However, the archive file still takes space on your computer or network drive.

What Is The Maximum Size For An Outlook Data File?

For Outlook 2016 and later, the default limit for .pst files is 50 GB. For .ost files (used with Exchange), the limit is also 50 GB. You can increase this limit by editing the registry, but it’s not recommended. Better to archive or delete.

Final Tips For Keeping Your Mailbox Clean

Once you’ve freed up space, maintain it. Here are some habits:

  • Delete emails you don’t need right after reading.
  • Unsubscribe from newsletters you never open.
  • Use rules to automatically delete or move certain emails.
  • Empty your Deleted Items folder weekly.
  • Save attachments to cloud storage before deleting the email.

By following these steps, you’ll never run out of space again. Your Outlook will run faster, and you’ll spend less time managing your inbox. Start with the Mailbox Cleanup tool today, and you’ll see results in minutes.

Remember, the key is consistency. A little effort each week prevents a big headache later. Now you know exactly how to free up space on outlook—put these tips into action and enjoy a clutter-free mailbox.