Mailbox Full? Find and Delete Large Email Attachments

TL;DR: In Gmail, search has:attachment larger:10M, delete what you do not need, then empty Trash. In classic Outlook, search messagesize:>5 MB or open File > Tools > Mailbox Cleanup; in new Outlook and Outlook on the web, Settings > Account > Storage shows each folder's size and deletes by age. Only classic Outlook can strip an attachment and keep the message. The attachments that fill a mailbox are documents that belong in storage anyway, so the lasting fix is to file them out as copies first, then delete freely.

A mailbox fills up with attachments, not with text. A few hundred scans, drawings and site photos and Gmail stops accepting mail or Outlook shows the quota warning. This guide covers the limits, how to find the heavy messages in Gmail and every version of Outlook, what deleting actually does, and a route that keeps the documents while the mailbox empties.

Disclosure: The Drive AI publishes this guide and is one of the routes compared at the end. Google, Microsoft and Clean Email facts come from their own pages, checked November 2, 2026.

What are the email attachment size limits?

Gmail accepts attachments up to 25 MB per message, and a larger file is sent as a Google Drive link instead. (Gmail attachment limits) Microsoft 365 mailboxes accept 35 MB sent and 36 MB received by default, and an administrator can set anything from 1 MB to 150 MB. (Exchange Online limits)

The same page sets the per-client ceilings: 150 MB in Outlook for Windows and Mac, 112 MB in Outlook on the web (112 MB for a classic attachment, up to 2 GB for a OneDrive attachment), 33 MB in Outlook for iOS and Android, and 250 attachments per message.

The limit that empties a mailbox is the quota, not the per-message cap:

• Gmail: 15 GB on a personal account, shared among Gmail, Google Drive and Google Photos. (Manage your storage)
• Outlook.com: 15 GB of email storage, separate from Microsoft cloud storage; Microsoft 365 consumer mailboxes are capped at 100 GB. Over the limit, Outlook.com stops sending and receiving. (Storage limits in Outlook.com)
• Work and school: 100 GB per user mailbox on Microsoft 365 Business Basic, Standard and Premium and on Enterprise E3 and E5; 50 GB on Office 365 E1 and Exchange Online Plan 1; 2 GB on F3 and Exchange Online Kiosk.

How do you find and delete large attachments in Gmail?

Search by size. Google's own storage page recommends has:attachment larger:10M for the biggest messages and filename:.pdf larger:5M for heavy PDFs; the number takes M for megabytes. (Manage your storage, Gmail search operators)

1. Run the search. Type larger:10M in the Gmail search box, and add older_than:1y to leave this year's mail alone. The free email attachment search builder prints the string if you would rather tick boxes.
2. Save what you need first. Download anything you may need again before the message goes; see how to download all attachments from Gmail.
3. Select and delete. Check the box to the left of each message and click Delete.
4. Empty Trash and Spam. Open Trash and click Empty Trash now. Until Trash and Spam are emptied, the messages still count against the quota.

Google One has a clickable version: go to one.google.com, click Storage, select Clean up space, pick a category, select the files and click Delete, then Permanently delete. (Clean up your Google storage) The broader operators are in how to find emails with attachments.

What does deleting an email do in Gmail?

A deleted message sits in Trash for 30 days, restorable until then, and is then permanently deleted. (Delete or recover Gmail messages) The storage figure can take up to 48 to 72 hours to update after a large clean-out.

Google documents no way to remove an attachment from a received message and keep the message. The two go together, which is why step 2 above comes before step 3.

How do you find large files in Outlook?

In classic Outlook, type messagesize:>5 MB in the search box, or open File > Tools > Mailbox Cleanup and use Find items larger than. (How to search in Outlook, Reduce the size of your mailbox)

1. Search by size. messagesize:>5 MB lists every message over 5 MB; combine it with received:"last year" or from: to narrow. The named sizes (messagesize:enormous for over 5 MB, and the rest) work in classic Outlook but are marked not supported in new Outlook for Windows.
2. Or open Mailbox Cleanup. Select the File tab, then Tools > Mailbox Cleanup. The dialog offers View Mailbox Size, Find items older than, Find items larger than, View Deleted Items Size, Empty Deleted Items, View Conflicts Size and Empty Conflicts. Microsoft's page applies to Outlook for Microsoft 365, 2024 and 2021, that is, classic Outlook.
3. Save, then delete or move. Download what matters (how to download all attachments from Outlook covers the bulk options), then delete the messages or move them to an Outlook Data File (.pst).
4. Empty Deleted Items. Mailbox Cleanup's Empty Deleted Items does it.

New Outlook and Outlook on the web. There is no Mailbox Cleanup. For a work or school account, open Settings > Accounts > Storage in new Outlook or Settings > Account > Storage on the web; the page shows each folder's size and lets you permanently delete everything in a folder, or only items older than 3, 6 or 12 months. Deleted Items counts until it is emptied. (Mailbox storage limits in Outlook) To see the heavy messages themselves, choose Sort > Has files, since the named size operators are not supported there.

Outlook.com. The same Storage page is at Settings > Account > Storage, with the same delete-by-age options; Deleted Items counts until emptied, or until Outlook.com removes the items itself after 30 days.

Can you remove an attachment from an Outlook email and keep the message?

Only in classic Outlook. Open the message, select the arrow next to the attachment name, choose Remove attachment, then close the message and save the changes; the email stays, lighter. In new Outlook, Outlook on the web and Outlook.com, Microsoft's instruction is to delete the email the attachment came with, after saving the file if you want it. (Remove or delete attachments in Outlook) It is one message at a time.

Does a cleanup tool like Clean Email help?

For grouping, yes; for deciding, no. Clean Email's Large Mail filter groups messages by size, showing groups over 1 MB by default with other thresholds a click away, so you can archive or delete a group at once. It states plainly that it cannot search message contents or attachments; its search covers sender names, addresses and subject lines, because message bodies are not downloaded. (Clean Email: searching and filtering) It starts at $9.99 a month or $29.99 a year, with a free tier, per its own site on November 2, 2026. (Clean Email)

It finds the heavy messages faster than a search box and still leaves you opening each one to decide. More of the field is in the roundup of email attachment management software.

Why not file the attachments out before deleting anything?

Because the attachments that make a mailbox large are documents that should live in storage anyway. A 10 MB scan of a signed contract is a contract that happened to arrive by email. Once a copy is filed under the counterparty's name, the message carrying it can go.

The Drive AI does that part. Connect the Gmail or Outlook account (Microsoft-hosted mailboxes only: Microsoft 365, Outlook.com and custom domains on Microsoft hosting), then:

• Run Historical Sync from the account's menu under Settings > Integrations, for the last 30, 90 or 180 days, or 365 on Outlook, with sent mail optional. Attachments are copied to the top level of the workspace as they are, scanned PDFs included. Images and calendar files are skipped, so a mailbox full of photos stays full.
• Let a workflow file the batch. A workflow that watches new uploads reads each file, names it by the vendor, client, date and type on the page, and files it into the folder your instructions name, in The Drive AI or a connected Google Drive, OneDrive, SharePoint or Dropbox, with a person approving anything you choose.
• Keep it going for new mail with an Email Attachment workflow, whose first step is always Save a Copy.

The mailbox itself is untouched. The Drive AI never deletes, moves or labels an email, and it does not shrink the mailbox; it makes deleting safe. After the sync, run the larger:10M or messagesize:>5 MB search above and delete, knowing the documents are filed elsewhere. Connected email needs Max or any Team plan; shared mailboxes nobody signs in to are not something it documents. The general method is in how to save email attachments to folders, and the feature page explains how to organize email attachments automatically.

Which route should you take?

If the problem is not space but a file that will not come down at all, that is a different fault: see Outlook attachments not showing or Gmail attachments not downloading for the documented causes.

Frequently Asked Questions

What is the email attachment size limit?

25 MB per message in Gmail, with larger files sent as Drive links. Microsoft 365 defaults to 35 MB sent and 36 MB received, adjustable by an administrator between 1 MB and 150 MB.

How do I delete large attachments in Gmail?

Search has:attachment larger:10M, download anything you need, check the messages and click Delete, then open Trash and click Empty Trash now. Google documents no way to remove an attachment and keep the message.

Gmail says storage is full but I deleted the emails. Why?

Deleted messages stay in Trash for 30 days and count against storage until Trash is emptied; Spam counts too, and the figure can take 48 to 72 hours to update. Gmail also shares its 15 GB with Google Drive and Google Photos, so the space may be elsewhere.

How do I manage large email attachments in Outlook?

In classic Outlook, search messagesize:>5 MB or use File > Tools > Mailbox Cleanup > Find items larger than, then delete, move to a .pst or remove the attachment. In new Outlook and on the web, Settings > Account > Storage shows each folder's size and deletes by age.

Can I remove an attachment from an Outlook email without deleting it?

In classic Outlook, yes: open the message, select the arrow next to the attachment, choose Remove attachment, and save on closing. New Outlook, Outlook on the web and Outlook.com require deleting the message.

Does The Drive AI delete emails to free up space?

No. It copies attachments out of a connected Gmail or Outlook account and files them by what they say; it never deletes, moves or labels a message. The mailbox shrinks only when you delete the messages afterwards, which is safe once the documents are filed.

File first, then delete

Run the size search to see how much of the mailbox is documents, then connect the account and let one Historical Sync copy them out and a workflow name and file them. Then delete the heavy messages without opening a single one. Start with a sample folder, or see how file workflows fit together first.