How to Find Large Emails in Outlook and Reclaim Space

The fastest way to find large emails in Outlook is a single search: type messagesize:>10 MB into the search box and press Enter. Outlook lists every message over that size in the current folder — switch the scope to All Mailboxes to check every folder at once, including Sent Items, which quietly holds a copy of everything you've ever sent with an attachment.

That one search usually turns up the handful of messages responsible for most of a bloated mailbox: an old conference deck, a screen recording someone forwarded twice, a PDF scan nobody needed after the meeting it was for. The rest of this guide covers the search operator in full, the Large Mail folder that keeps watching after today, and the order that clears the most space with the least clicking.

Before you start#

A few things to check before you start deleting, because clearing the wrong item costs more time than it saves.

• Confirm you actually have a size problem. Go to File > Info in classic Outlook, or Settings > Accounts > Storage in new Outlook and Outlook on the web, to see your current mailbox size against your quota.
• Check whether a retention policy or legal hold applies to your mailbox. If it does, deleting a large email will not free the space you're expecting — see the warning below.
• Decide if you need the attachment at all. Some of the biggest space users are meeting recordings, screen captures, or design exports that someone else already has the master copy of.

Steps: find and clear the largest messages#

Work through these in order. Each step either finds more space or makes the next step safer.

1. 1

   Check your total mailbox size

   Open File > Info in classic Outlook, or Settings > Accounts > Storage in new Outlook and Outlook on the web, to see how close you are to your quota. Exchange Online Plan 1 mailboxes get a warning at 49 GB and stop accepting new mail at 50 GB; Plan 2 doubles both thresholds. Knowing the number tells you whether you need to clear 200 MB or 20 GB.

2. 2

   Search with the size operator

   In the search box, type messagesize:>10 MB (or >25 MB if you're badly over quota) and press Enter. Change the search scope from Current Folder to All Mailboxes to catch Sent Items and any secondary folders — Sent Items is usually the biggest surprise, since every attachment you've ever sent lives there too.

3. 3

   Sort the results and open the worst offenders

   Click the results list's Size column, or use Arrange By > Size, to put the largest messages on top. Open the top five or ten before deleting anything — a 40 MB message is sometimes a single embedded image inflated by a signature logo, not the video file you assumed.

4. 4

   Strip the attachment, or delete the whole message

   If the text of the email still matters but the file doesn't, right-click the attachment in the message's Attached box and choose Remove — classic Outlook keeps the message and drops the file. New Outlook doesn't have this option yet, so delete the whole message there instead if the attachment is the problem.

5. 5

   Empty Deleted Items to actually reclaim the space

   Deleting a message moves it to Deleted Items, which still counts against your quota until you empty that folder too. Right-click Deleted Items and choose Empty Folder. This is the step people forget, and it's why a mailbox can stay full after a long deleting session.

6. 6

   Build a Large Mail search folder so it doesn't creep back

   In classic Outlook, right-click Search Folders in the folder pane, choose New Search Folder, and pick Large Mail from the built-in list, then set a size threshold. It sits in your folder pane permanently, always showing the current worst offenders. New Outlook is rolling the same template into Settings > Search Folders; Outlook on the web has no search folders at all, so sort a folder by size there instead.

How this differs across Outlook#

Not every method exists on every version, and that's the biggest source of confused advice online — a right-click option a colleague swears by may simply not be built into whichever Outlook you're running.

What to do when it doesn't work#

• Search returns nothing, but you know a huge message exists: the search index is out of date. Rebuild it from File > Options > Search > Indexing Options > Advanced > Rebuild, then wait — a large mailbox can take hours to reindex.
• The listed size looks small for a message you're sure has a huge attachment: open the message and check its Properties for the real size. A long forwarded chain sometimes shows only the newest reply's size in the list view, not the whole thread.
• You deleted the message and your quota didn't move: empty Deleted Items first, and if it still hasn't changed, ask an admin whether the mailbox is on a retention or litigation hold — see the warning earlier in this guide.
• The big file is a shared link, not an attachment: Outlook increasingly sends large files as OneDrive links instead of raw attachments. A OneDrive-linked file can be up to 2 GB — more than triple the roughly 112 MB ceiling for an attachment sent through Outlook on the web — and it barely touches your Exchange quota, because the file itself lives in OneDrive, not your mailbox.

A faster way: stop hunting for this manually#

Everything above works, and it's worth knowing even if you never repeat it — quotas creep back up. The manual version means running this search again every few months, on every account you own.

AI Emaily's smart search understands a request like "show me the biggest attachments from the last year" across every connected mailbox at once, not one Outlook profile at a time, so a large-file problem spread across a Gmail and an Outlook account surfaces in one place instead of two separate searches. We build AI Emaily, and this is one of the plainer jobs the agent does well — not writing your replies, just doing the finding you'd otherwise do by hand. It's a 7-day free trial on the Pro plan if you want to see whether it replaces the quarterly cleanup ritual.