If you are getting a "mailbox full" warning or your emails are bouncing back, your email storage has hit its limit. This guide covers how to find what is eating your space, clean it up, and keep it from filling up again.

How email storage works

Every email account has a storage limit. When you hit it, you stop receiving new emails and cannot send anything. Here is what you are working with:

• Gmail (free): 15 GB shared across Gmail, Google Drive, and Google Photos. That 15 GB is not just email – a full Google Drive or photo library eats into your email space too
• Gmail (Google Workspace): 30 GB to 5 TB depending on your plan
• Outlook.com (free): 15 GB for email
• Microsoft 365 (work/school): 50 GB to 100 GB depending on your plan
• iCloud Mail: 5 GB shared with iCloud Drive, Photos, and device backups
• Yahoo Mail: 1 TB for email

The biggest space hogs are almost always attachments. A single email with a 25 MB PDF takes up more space than hundreds of plain text emails combined.

Find and delete large emails in Gmail

The fastest way to free up space in Gmail is to find the biggest emails and delete them.

Search for large emails:

1. Open Gmail in a browser
2. In the search bar, type size:10MB and press Enter. This shows all emails larger than 10 MB
3. To find even larger ones, try size:25MB or size:50MB
4. To find large emails with attachments specifically, search has:attachment size:5MB
5. Review the results and delete emails you no longer need

Search for old large emails:

• older_than:1y size:5MB finds large emails more than a year old
• older_than:2y has:attachment finds emails with attachments older than two years

Empty the Trash:

1. After deleting emails, go to Trash in the left sidebar
2. Click Empty Trash now at the top. Emails in Trash still count toward your storage until they are permanently deleted
3. Gmail automatically empties Trash after 30 days, but if you need space now, do it manually

Check your full Google storage breakdown:

1. Go to one.google.com/storage in your browser
2. This shows how your 15 GB is split between Gmail, Drive, and Photos
3. If Drive or Photos is the real problem, clean those up too. Large files in Google Drive trash also count against your quota until permanently deleted

Find and delete large emails in Outlook

Outlook on the web (outlook.com or Outlook Web App):

1. Open Outlook in a browser
2. In the search bar, type size:>10MB and press Enter to find large emails
3. You can also try hasattachment:yes size:>5MB to target attachments specifically
4. Select and delete emails you do not need

Outlook desktop app (Windows):

1. Open Outlook and go to File > Info
2. Click Tools > Mailbox Cleanup
3. Click View Mailbox Size to see which folders are using the most space
4. Use Find items larger than to search for big emails. Set a size (like 5000 KB) and click Find
5. Delete what you do not need and empty the Deleted Items folder afterward

Outlook desktop app (Mac):

1. There is no built-in mailbox cleanup tool on Mac Outlook
2. Use the search bar and type size:>10MB to find large emails manually
3. Sort by size in list view to identify the biggest items
4. Delete and empty the Deleted Items folder

Empty Deleted Items:

Right-click the Deleted Items folder and select Empty Folder. Like Gmail's Trash, deleted emails still count toward your quota until they are permanently removed.

Archive vs delete: which should you use?

Archiving removes an email from your inbox but keeps it in your account. The email is still searchable and still counts toward your storage limit. Archiving is for emails you want out of sight but might need later.

Deleting moves an email to Trash. Once you empty the Trash, the email is gone permanently and frees up storage space.

If you are trying to free up space, archiving does nothing. You need to delete.

Use archiving for emails you might need to reference later (receipts, contracts, important conversations). Use deletion for newsletters, notifications, promotional emails, and anything with large attachments that you have already saved elsewhere.

Reduce future storage use

Download attachments and delete the email:

If someone sends you a large file you need to keep, download the attachment to your computer (or save it to cloud storage), then delete the email. You keep the file without it counting against your email quota.

Unsubscribe from newsletters:

Newsletters with images and formatting add up over time. Scroll to the bottom of any newsletter and click Unsubscribe. In Gmail, you can also click the Unsubscribe link that appears next to the sender's name at the top of the email.

Use links instead of attachments:

When sending files, upload them to Google Drive, OneDrive, or Dropbox and share a link instead of attaching the file directly. This keeps the file out of both your and the recipient's email storage.

Set up filters to auto-delete:

In Gmail, you can create filters that automatically delete emails from certain senders (like daily notification digests) so they never accumulate. Go to Settings > Filters and Blocked Addresses > Create a new filter.