How to Find and Delete Large Emails in Outlook

A handful of emails with big attachments can eat hundreds of megabytes — and they’re the fastest way to free up space when your mailbox is near its limit. Here’s how to find your largest emails in every version of Outlook and clear them safely.

Method 1: Sort by size (Outlook.com & new Outlook)

Open the folder you want to check (start with your Inbox and Sent Items).
Click the sort control (Filter → Sort → Size, or the column header).
The biggest emails jump to the top — review them and delete or save-then-delete.
Empty Deleted Items afterward, or the space isn’t actually freed.

Method 2: Mailbox Cleanup (classic Outlook desktop)

Classic Outlook has a purpose-built tool:

File → Tools → Mailbox Cleanup.
Choose Find items larger than and enter a size (try 5000 KB = 5 MB).
Click Find to list every large item across the mailbox.
Delete what you don’t need, then empty Deleted Items.

You can also Find items older than here to combine size and age.

Method 3: Filter for messages with attachments

Attachments are usually the culprit:

In the search bar, type hasattachments:yes (add larger:5MB in classic Outlook).
Sort the results by size.
Save any attachments worth keeping (to OneDrive or your PC), then delete the emails.

Don’t forget Sent Items and other folders

Large files you sent count too. Check Sent Items, Drafts, and any archive folders — big attachments often hide there long after you’ve forgotten them.

Size is only half the story

Sorting by size finds a few big emails, but on most mailboxes the space is actually taken by thousands of small emails from a few noisy senders — not one giant attachment. Clearing those is the bigger win.

Sender Sweep scans your whole Outlook mailbox and ranks every sender by how many emails they’ve sent, so you can clear the accounts filling your quota — the newsletter with 4,000 messages, not just the one 20 MB attachment — in a single click, right in your browser. Pair it with the size sort above and you’ll reclaim the most space in the least time.

FAQ

How do I find the biggest emails in Outlook? Sort a folder by Size, or use Mailbox Cleanup → Find items larger than in classic Outlook. Check Sent Items too.

Does deleting large emails free up space immediately? Only after you empty Deleted Items — deleted mail sits there (and counts toward your quota) until you do.

What if I want to keep the attachment but not the email? Save the attachment to OneDrive or your computer first, then delete the email to reclaim the space.