How to Sort Emails by Size in Outlook on the Web (and Find the Big Ones)

By the end, my Bluebird Landscaping “Clients” folder shows the Oak Street site photos email, the one eating about 2 MB, sitting alone at the top of the list under a “Large (1 – 5 MB)” heading.

In this tutorial, I’ll show you how to sort emails by size in Outlook on the web, how to flip the order, how to narrow the list to emails with files, and what the size groups actually tell you.

The same sort button sits at the top of the message list in the new Outlook for Windows, too.

What you need before you sort

I tested everything in a Microsoft 365 work mailbox for my made-up business, Bluebird Landscaping Co. Here’s what you need:

• Outlook on the web (outlook.office.com) or the new Outlook for Windows. Both use the same control at the top of the message list.
• A folder with some mail in it. I used a folder called Clients with seven emails: two with inline photos, one with three attached emails, and four short plain-text ones.
• A reason to look. Usually it’s a storage warning. If you’re not sure how close you are, first check your storage space in Outlook so you know how much you need to clear.

One heads-up: this post is about Outlook only. If a search for “sort by size” brought you here for Gmail or Yahoo, their menus work differently.

Sorting the Clients folder by size

Sorting is set per folder, so start by opening the folder you want to clean up. I clicked Clients in the folder pane on the left. If your folder list is a mess, you can reorder the folders in Outlook Online so the big ones are easy to reach.

Open the sort menu above the message list

Right above the list of emails, next to the folder name, there are two small buttons. The one with up and down arrows is the sort button. Click it, and a menu opens with a “Sort by” section and a “Sort order” section.

Mine was on the default: Date checked, with Newest on top. The Sort by list has Date, From, Category, Flag status, Flag due date, Size, Importance, Subject, and Type.

Pick Size to group emails by how big they are

Click Size. The menu closes and the list regroups right away. Instead of Today, Yesterday, and Last week, you get headings named after size ranges.

In my folder, the Oak Street site photos email landed alone under Large (1 – 5 MB). Everything else sat under Medium (25 KB – 1 MB), starting with the Hillcrest HOA planting plan and the “May 2026 emails to save” message.

Even my short plain-text emails, like the Crew schedule for the week of May 11, 2026, showed up in Medium. There was no smaller group in my folder, so don’t expect every tiny note to sit in its own bucket.

Switch between largest and smallest on top

Open the sort button again. Once Size is checked, the Sort order labels change to Smallest on top and Largest on top. Largest on top was already selected for me, which is what you want when you’re hunting for space.

I clicked Smallest on top just to see it. The Medium group moved to the top, led by the plain-text emails like the Riverside Cafe patio planter quote and the Oak Street mulch delivery receipt.

Smallest on top is handy if you want to keep the heavy photo emails and quickly clear out short notes, but most people will switch straight back to Largest on top.

Filter to emails that have files

The button just left of the sort button, with three lines on it, is the Filter button. Click it and you’ll see All, Unread, Flagged, To me, Has files, Mentions me, and Has calendar invites.

I chose Has files. The filter icon picked up a little paperclip, and the list dropped to the three emails with pictures or attachments. Because the size sort was still on, the Large group stayed on top.

This is the fastest view for cleanup. The plain-text mail is out of the way, and the biggest file-heavy emails are first. If you want to keep one before you delete it, you can download the Outlook email to your computer first.

Check that the size sort worked

A few quick things told me the sort was really on:

• The group headings in the list say Large (1 – 5 MB) and Medium (25 KB – 1 MB) instead of dates.
• The sort menu shows Size checked and Largest on top selected.
• When I left Clients and came back later, it was still sorted by size. The Has files filter, on the other hand, had reset to All.
• My Inbox was still sorted by Date, because the setting applies only to the folder you change.

Keep in mind that the message list doesn’t show an exact size for each email. You only see the range in the group heading, so two emails in Medium could be 30 KB or 900 KB.

Also, deleting a big email doesn’t free the space right away. Microsoft says the Deleted Items folder still counts against your mailbox storage until you empty it, so clear that folder when you’re done.

Change it for your own mailbox

You don’t need my folder setup. Here’s how I’d adapt it:

• Sort every folder you clean. Since it’s per folder, repeat the steps in Inbox, Sent Items, and any project folders. Sent Items often hides the photos you sent out yourself.
• Turn on Has files first when the folder is huge. It cuts the list down to the messages that actually take up room.
• Go back to Date when you’re finished. Open the sort button, choose Date, and pick Newest on top so new mail shows up where you expect it.
• Move mail before you delete it. If several big emails belong to one job, you can forward multiple emails at once to a coworker, then remove them from your mailbox.

To keep big attachments from piling up again, you can create inbox rules in Outlook Online that file messages from certain senders into their own folder, then sort just that folder by size each month.

I didn’t test classic Outlook for Windows, Outlook for Mac, or the mobile apps for this post. Microsoft’s guide says classic Outlook has its own Filter dropdown on the message list, but the menus there look different, so I won’t guess at the clicks.

More ways to tidy up Outlook

• Clear your recent searches in Outlook
• Save Outlook emails to OneDrive
• Shrink images before you send them
• All Outlook Online tutorials

Questions about this setup