How to Clean Up Outlook Mailbox in Classic and New Outlook

Key Takeaways

• In classic Outlook for Windows, go to File → Info → Tools → Mailbox Cleanup to view mailbox size, find old or large items, run AutoArchive, and empty Deleted Items.
• New Outlook and Outlook on the web use the Storage page instead (Settings → Accounts → Storage). You can delete all items in a folder, or only items older than 3, 6, or 12 months.
• Clean Up Conversation removes repeated messages in one thread. Clean Up Folder does the same for a whole folder.
• Deleted emails still count toward your storage until Deleted Items is emptied.
• Clean Email finds your oldest and largest emails, deletes them in bulk, and sets rules so the mailbox doesn't fill up again — on web, Mac, iPhone, and Android.

Select Your Issue for Fast Assistance

• How do I quickly clean up my Outlook mailbox?
• How to clean up Outlook mailbox without deleting emails?
• How do I clean up Outlook to run faster?
• How do I clean up thousands of emails in Outlook?
• What does the Cleanup button do in Outlook?
• Does Clean Up in Outlook remove attachments?
• What is the difference between Clean Up Conversation and Clean Up Folder?
• What is the best way to clean up Outlook mailbox?
• How do I declutter my Outlook email?
• How do I free up space in my Outlook mailbox?
• How do I empty my inbox in Outlook?
• How to clean up Outlook mailbox in Office 365?
• Why is my Outlook mailbox storage full after deleting everything?
• Where is Mailbox Cleanup in new Outlook?

How to Check Your Outlook Mailbox Size

Every Outlook mailbox has a storage limit. Free Outlook.com accounts get 15 GB for email. Work and school mailboxes can have up to 100 GB, depending on the plan and admin settings. When the mailbox is full, you can't send or receive email.

⚠️ If you’re seeing an Outlook mailbox full message, it’s time to manage old and unnecessary emails. For a full fix, see what to do when your Outlook mailbox is full.

To check how much space you have left, check your mailbox size by following these steps (if you have an Outlook client through Microsoft 365 or use Outlook 2021, Outlook 2019, Outlook 2016, or Outlook 2013):

1. From your mailbox, select your account.
2. Then click on Folder → Folder Properties.
3. In the Inbox Properties window, click the button that says Folder Size.
4. Once the box opens, you will see the total size of your Inbox and all of the subfolders you have set up.

As you’ll learn below, you can also access your mailbox size through Outlook Mailbox Cleanup, which gives you several other tools to help you keep your email account clean. In new Outlook and Outlook on the web, open Settings → Accounts → Storage (steps in the Mailbox Cleanup in New Outlook section below).

Using Outlook Mailbox Cleanup Tool in Classic Outlook for Windows

Outlook Mailbox Cleanup is a section within the classic Outlook desktop app for Windows that has tools specifically designed to help you clean up Outlook inbox easily and effectively. In fact, you can use the handy Outlook Mailbox Cleanup tools to review the size of your inbox, clear out specific items based on criteria such as the email size or date received, and archive items.

How to use Mailbox Cleanup in Outlook

To access Outlook Mailbox Cleanup, open your Outlook desktop client, then navigate to File → Info → Tools → Mailbox Cleanup.

⚠️ You won't find Mailbox Cleanup in new Outlook or Outlook on the web. If you use one of them, jump to Mailbox Cleanup in New Outlook and Outlook on the Web below.

From here, you will have options to use any of the following tools, each of which is outlined below:

1. View Mailbox Size

While this tool is fairly self-explanatory, it is helpful to know how much space your inbox is taking up, along with what large emails might be tucked away in certain folders.

To view your Outlook mailbox size:

1. Go to File at the top of your desktop application.
2. Select Info on the left side, then click Tools in the center.
3. When the drop-down menu appears, click Mailbox Cleanup.
4. When the dialog box appears, click the button that says View Mailbox Size.
5. Like the previous directions, you will now see the total mailbox size and each subfolder’s size in KB.

When looking at your subfolders, pay close attention to any that look significantly larger than others. This can help you see areas where you may need to delete items that are no longer needed. Also, consider subfolders you may not typically think about as data hogs, like your calendar or contact list — there may be old appointments or old contacts you no longer need.

In addition to the contents stored locally, you can also view the storage in your mail server (assuming you have one). To do this, just click the tab at the top of the mailbox size box that says Server Data instead of Local Data. This can be an important place to check periodically if your emails automatically archive to the server.

2. Find Items Older Than a Certain Date or Larger Than a Certain Size

Besides checking the amount of data each folder contains within your inbox, you can also hunt down specific messages based on dates or message size by using the ‘Find’ function within these tools. In fact, this is an easy way to free up storage in Outlook without spending hours looking through each subfolder in your mailbox.

To use this tool, simply select whether you’d like to search for emails older than a certain number of days or all messages larger than a certain size. Then, input your data parameters (i.e. ‘older than 90 days’ or ‘larger than 500KB’) and push the Find button on the right.

After this, an advanced find window will appear. You can use this to narrow down your search results even further, or you can simply scroll through the messages your desktop client found based on your initial criteria. On the right side of each message, you’ll have the option to flag it for follow-up or delete the message completely.

You can also click on the message to open it, or right-click on the email to see more options like ‘quick print’, ‘forward’, ‘move’, and more. You can even use Shift + Click to highlight multiple messages and perform the same action to them all, which can really save you time. This is a great way to delete multiple emails in Outlook.

3. Archive Items by Using AutoArchive (Classic Outlook for Windows)

Many people use email archiving to clean Outlook inbox while still maintaining certain messages so they can quickly retrieve them at a later date through a simple search. This can be a valuable tool for anyone who knows how to use it to their advantage.

Although you may already know how to archive in Outlook, the AutoArchive tool can help you quickly store items based on your set parameters. However, AutoArchive doesn’t have any pre-established archiving rules. This means you will need to set these up if you plan to use AutoArchive regularly. AutoArchive moves old items into a separate Outlook Data File (.pst) on your computer, so it frees up space in your mailbox.

⚠️ The AutoArchive tool is available in Outlook for Windows but is not present in Outlook for Mac, Outlook Web App (OWA), or Outlook mobile apps.

To set up AutoArchive parameters:

1. Open your desktop client and click on File in the top menu.
2. Select Options from the list.
3. In the Options menu, navigate to the Advanced tab. Under the AutoArchive section, click on AutoArchive Settings.
4. Then set how frequently you want AutoArchive to run. For example, you can choose to run it monthly, quarterly, etc.
5. Decide which emails should be archived. For instance, you can choose to archive messages older than 12 months. Specify where the archived emails will be moved. You can choose a specific folder or opt to have them permanently deleted.
6. After completing these steps, your inbox will automatically apply these rules each time you use the AutoArchive function in Mailbox Cleanup.

4. View Deleted Items Size

Did you know that pushing ‘delete’ on messages doesn’t permanently remove them from your inbox? Instead, it simply places them in the Trash, which you still need to empty. So, if you’re trying to figure out how to clean up Outlook inbox but realize archiving isn’t helping you reduce the inbox size, that’s why.

Thankfully, Outlook Mailbox Cleanup offers the option to view the size of your discarded messages before you permanently delete them with the View Deleted Items Size tool.

Like the View Mailbox Size feature, this tool breaks down how much space (in KB) your trash is taking up. If it’s pretty bad, then you can simply use the Empty button under this Mailbox Cleanup tool to clear out all that discarded clutter. Just remember, once an email is removed from your trash, it’s gone for good.

5. View Conflicts Size

The last tool within Outlook Mailbox Cleanup is called View Conflicts Size. This is essentially a storage area for emails Outlook thinks overlap with other messages in your folders because of similarities in things like the subject line or attachments.

If you click the View Conflicts Size button, you will see a filtered view of your mailbox with only messages Outlook has flagged as conflicts. Most of the time, these messages can be deleted, but it’s always best to double-check before you completely erase anything.

How to Use Clean Up Conversation and Clean Up Folder

Clean Up is a separate tool from Mailbox Cleanup. It removes redundant messages: older replies whose full text is already quoted in a later reply in the same thread.

1. In classic Outlook, go to the Home tab.
2. In the Delete group, select Clean Up. In the simplified ribbon, select the arrow next to Delete.
3. Choose Clean Up Conversation, Clean Up Folder, or Clean Up Folder & Subfolders.

Clean Up Feature and Attachments

Outlook's Clean Up feature is designed to remove redundant messages in email conversations, but it does not delete attachments from the remaining emails.

However, you can remove attachments from emails in Outlook without deleting the emails themselves. This feature is available in Outlook for Microsoft 365, Outlook 2019, Outlook 2016, and Outlook 2013.

Clean Up Conversation vs Clean Up Folder

Clean Up Conversation removes redundant messages from a single email thread. It keeps only the latest message in the conversation that contains all previous replies, clearing unnecessary clutter.

Clean Up Folder, on the other hand, applies the same process to an entire folder, removing redundant messages across all conversations within that folder. This is useful for decluttering large email folders in bulk. Clean Up Folder & Subfolders does the same for the folder and every subfolder inside it.

Cleaned-up messages go to Deleted Items by default, so empty that folder afterward to actually free up space. To change the destination folder, or to keep flagged, categorized, or unread messages, go to File → Options → Mail → Conversation Clean Up.

Mailbox Cleanup in New Outlook and Outlook on the Web

New Outlook for Windows and Outlook on the web don't have the Mailbox Cleanup button. Instead, they have a Storage page. It shows how much space each folder uses and lets you clear a folder in a few clicks.

1. Select Settings (the gear icon) at the top of Outlook.
2. Go to Accounts → Storage. In Outlook.com, you can also type “Storage” in the Settings search box.
3. Check how much space each folder uses.
4. Below the list, pick a folder and choose to delete all its items, or only items older than 3, 6, or 12 months.

⚠️ Items you delete from the Storage page are deleted permanently.

A few things to know about storage in Outlook.com:

• Deleted Items count toward your storage until you empty the folder. Outlook.com also removes them automatically after 30 days.
• Junk Email is deleted automatically after 10 days.
• Attachments count toward your Microsoft cloud storage (5 GB free, shared with OneDrive), not the 15 GB email limit.

Use Sweep in Outlook on the Web and New Outlook

Sweep clears out email from one sender in a few clicks. It works well for newsletters, receipts, and notifications that pile up.

1. Select an email from the sender you want to clean up.
2. On the menu bar, select Sweep.
3. Choose what to do: delete all email from this sender (including future email), keep only the latest email, or delete email older than 10 days.
4. Select Sweep to apply it.

Keep in mind:

• Sweep rules run once a day, not the moment new email arrives.
• Sweep doesn't work in Junk Email, Drafts, Sent Items, or Deleted Items.
• Swept emails go to Deleted Items and still count toward your storage until you empty that folder.

For setup details and how to edit Sweep rules, see our guide to Outlook Sweep rules.

More Ways to Free Up Space in Outlook

These quick fixes free up more space and keep your mailbox from filling up again. For tips on keeping things tidy afterward, see how to organize email in Outlook.

1. Compact your Outlook data file

Moving emails to the Archive folder doesn't make your mailbox smaller, because that folder is still part of it. For archiving steps, see how to archive in Outlook.

In classic Outlook, all of your email account information is stored in an Outlook Data File (.pst) if you are using a POP account, and Offline Outlook Data File (.ost) if you are using an Microsoft 365, Exchange, Outlook.com account, or IMAP account.

You can, however, compress this file by following these steps on Outlook 2013 and newer versions:

1. Delete any items and empty the Deleted Items folder.
2. Click File → Account Settings → Account Settings.
3. On the Data Files tab, click the file you’d like to compact, then click Settings.

💡 Note: If you use an Outlook.com or Exchange email account, you must also click on the Advanced tab, then select Outlook Data File Settings.

4. Now, click Compact Now and then click OK.

2. Store attachments outside your mailbox

Unfortunately, attachments take up lots of unnecessary space in your Outlook inbox, especially if you hold onto the emails just to access the attachments time and time again.

However, you can avoid this! One practical solution for how to reduce mailbox size without deleting emails is to store attachments outside your mailbox so they aren’t filling up Outlook and wasting storage space.

In classic Outlook:

1. Launch the Outlook desktop client on your computer.
2. Select the message you’d like to download attachments from.
3. Click on the downward arrow to open the list of options and choose Save All Attachments.
4. Now, choose the location you want to store attachments outside of the mailbox, such as a folder on your desktop or your Documents folder.
5. The attachments will then download to the chosen location, where you can access them anytime.
6. Remove the attachment from the email, or delete the email, and empty Deleted Items.

In new Outlook and Outlook on the web, sort the folder by size, select Save to OneDrive under the attachment, and then permanently delete the original email.

3. Empty the Deleted Items folder

Most people assume that when you delete an email, it disappears and that’s it. However, it first goes to the Deleted Items folder (trash), which you have to then empty. To do this, simply right-click on the Deleted Items folder (or Trash folder depending on the version of Outlook you use), then select Empty Folder.

If you’d rather have a ‘set it and forget it’ approach to emptying your deleted items, you can also delete emails in Outlook automatically by using these steps:

1. From Outlook on your desktop, navigate to File → Options.
2. Click on the Advanced tab, then look for Outlook Start and Exit section.
3. Check the box labeled Empty Deleted Items folders when exiting Outlook.
4. Press OK to confirm.

To skip Deleted Items altogether, select the emails and press Shift + Delete to delete them permanently.

4. Empty the Junk Email folder

Just like with the Deleted Items folder, the Junk Email folder can also end up with a lot of messages you forget exist. This can take up valuable space in your mailbox, so you may want to delete these periodically as well to save yourself some space.

To do this, you can simply right-click on the Junk Email folder on the left side of the Outlook web app and select Empty Folder from the options listed.

5. Delete All Emails in Outlook

If clearing the Deleted Items folder has you wondering how to delete multiple emails in Outlook or even all of them, Outlook’s native features can help.

You can quickly select and delete emails by clicking on a folder, pressing Ctrl + A (or Command + A on Mac) to select all messages, and then pressing the Delete button or clicking Empty folder on the right. This allows you to remove emails in bulk directly from any folder.

However, for larger mailboxes, this process can be tedious and still requires manual cleanup of the Deleted Items folder.

For a faster and more convenient solution, Clean Email makes it simple to select all emails in any folder and delete them in just a few clicks:

1. Navigate to the folder you want to clean.
2. Use the Select All feature to highlight all emails in the folder.
3. Choose Delete to permanently remove them, bypassing the need to clear them again from the Deleted Items folder.

⚠️ Warning: Deleting emails with this method is permanent and cannot be undone. Make sure to review your selection carefully before proceeding.

Wrapping Up

Classic Outlook gives you the most built-in help: Mailbox Cleanup, AutoArchive, and Clean Up. In new Outlook and on the web, the Storage page does the same job with fewer options. To clear thousands of emails at once, or to stop the mailbox from filling up again, try Clean Email: it works on any device and keeps cleaning with rules after you're done.