Your Outlook mailbox is full, preventing you from sending new messages. Large emails with attachments are the most common cause of a full mailbox. This article explains how to locate and remove these space-consuming items. You will learn to use Outlook’s built-in search tools and folder size reports to clean up your storage.
Key Takeaways: Finding and Removing Large Outlook Items
- Search > Search Tools > Size > Large (1-5 MB): Filters your current folder view to show only emails larger than 1 megabyte for quick review.
- File > Info > Mailbox Cleanup > View Mailbox Size: Opens a detailed report showing folder sizes and the largest individual items in your mailbox.
- Search box query “size:>5MB”: A manual search syntax to find all items larger than a specific file size threshold you define.
How Outlook Manages Mailbox Size and Large Items
Microsoft Outlook stores your emails, calendar entries, and contacts in a data file on your computer or on a Microsoft 365 server. Every item, especially those with file attachments, uses a portion of your allocated mailbox storage quota. When this quota is reached, you cannot send new emails until you create space.
Outlook provides several tools to identify large items without manually checking every email. The primary methods are the search filter for size and the Mailbox Cleanup utility. These tools scan your mailbox’s index to quickly sort items by their file size. Using them is the fastest way to target the emails consuming the most space.
Understanding Attachment Size vs. Total Item Size
When you search for large items, Outlook reports the total size of the email. This includes the message text, formatting, and any embedded images or attachments. A 2 MB PDF file attached to an email will make the entire email item report as larger than 2 MB. Focus on items with the largest total size for the most significant space recovery.
Steps to Find Large Emails Using Search Filters
The quickest method is to use the size filter in the Outlook ribbon. This works in any mail folder, such as your Inbox or Sent Items.
- Navigate to the mail folder you want to check
Click on your Inbox, Sent Items, or the entire mailbox folder at the top of your folder list. - Click the Search box at the top of the message list
Clicking the box that says “Search Current Mailbox” will activate the Search Tools tab on the ribbon. - Go to Search Tools > Search > Size
On the ribbon, click the Search Tools tab. In the Refine group, click the Size button. - Select a size category from the menu
Choose Large (1-5 MB), Very Large (5-10 MB), or Huge (>10 MB). Outlook will immediately filter the list to show only emails in that size range. - Review and delete the large emails
Select one or more emails from the filtered list. Press the Delete key on your keyboard or right-click and select Delete to move them to the Deleted Items folder.
Using the Mailbox Cleanup Tool for a Detailed Report
For a comprehensive view of what is using space, use the Mailbox Cleanup dialog. This tool shows folder sizes and lists your largest individual items.
- Go to File > Info
In Outlook, click the File tab in the top-left corner to open the Backstage view. The Info section is selected by default. - Click the Mailbox Cleanup button
In the Account Information section, find and click the Mailbox Cleanup button. This opens a new dialog window. - Click View Mailbox Size
In the Mailbox Cleanup dialog, click the View Mailbox Size button. A new window titled Folder Size will open. - Review the folder sizes and largest items
The Folder Size window has two tabs. The Folder Size tab lists all your folders and their total size. Click the Server Data tab to see a list of your largest individual email items, sorted by size. - Find and delete items from the list
In the Server Data list, note the location of large items. Close the windows, navigate to that folder, and use the search size filter to locate and delete the specific email.
Common Mistakes and Limitations When Cleaning Mailbox Space
Forgetting to Empty the Deleted Items Folder
Deleting emails only moves them to the Deleted Items folder. They still count against your mailbox quota. Right-click the Deleted Items folder and select Empty Folder to permanently remove them and free up space. You can also set Outlook to empty this folder automatically when closing the program via File > Options > Advanced > Outlook start and exit.
Not Checking All Mail Folders Including Archives
Large emails might be in archived .pst files or other custom folders. Use the search size filter in the All Mail Items view or check each data file separately. For local archive files, you can view their properties by right-clicking the root of the archive in the folder pane and selecting Data File Properties > Folder Size.
Overlooking Calendar and Contact Attachments
Large files can be attached to calendar events or contact entries. These are not found by searching mail folders. Use the Folder Size report from Mailbox Cleanup to see the size of your Calendar and Contacts folders. If they are large, open those folders and use the search box with the size:>1MB syntax.
Manual Search vs. Automated Tool Comparison
| Item | Search Size Filter | Mailbox Cleanup Tool |
|---|---|---|
| Primary Use | Quick filtering within a single folder | Comprehensive mailbox analysis and reporting |
| Speed | Instant results using the local index | Slower, requires querying the server or data file |
| Best For | Targeted cleanup of known folders like Inbox | Identifying the root cause of a full mailbox quota |
| Shows Folder Sizes | No | Yes, in a detailed table |
| Finds Largest Single Items | Only within the applied filter | Yes, provides a ranked list across all folders |
You can now efficiently locate and remove large emails to solve mailbox quota errors. Start by using the Size filter on your Sent Items folder, as sent emails with attachments are often the largest. For ongoing management, schedule a monthly review using the Mailbox Cleanup tool’s View Mailbox Size feature. An advanced tip is to create a search folder using the query “hasattachments:yes size:>2MB” to always have a dynamic view of your largest items with attachments.