Search guides

Fix a Mac that has Mail full

We'll empty trash, find large messages, and archive or delete old mail—or rebuild the mailbox if it is corrupted.

Troubleshooting · Home maintenance
10–25 min
What you'll need
  • Mail app
  • External drive (optional, for archiving)
Step 1 of 5

Quick triage — pick your path

Get started

Choose the option that matches what you see. You can jump straight to that section.

Show full guide

Steps

Goal: Free disk space used by Mail.

  • Empty Mail trash.
  • Sort by size and delete or archive large messages.
  • Archive old mailboxes to an external drive.
  • Rebuild the mailbox if corrupted.

Empty trash

Goal: Remove deleted messages from disk.

  • Mail → Empty Trash.
  • Good: Trash empty. Proceed to Find large messages.
  • Bad: Trash already empty—check large messages.

Find large messages

Goal: Identify and remove messages with large attachments.

  • View → Sort By → Size. Delete or archive the largest messages.
  • Good: Space freed.
  • Bad: No large messages—archive old mailboxes.

When to get help

Call a pro if:

  • The mailbox is corrupted and Rebuild fails.
  • You need to recover deleted mail.

Verification

  • Mail storage decreases (check About This Mac → Storage).
  • Trash is empty.
  • Mail opens and loads normally.

Escalation ladder

Work from the device outward. Stop when the problem is fixed.

  1. Empty trash Mail → Empty Trash.
  2. Remove large messages Sort by size; delete or archive messages with attachments.
  3. Archive and rebuild Export mailboxes; rebuild if corrupted.
  4. Call a pro Corrupted mailbox or need recovery.

What to capture if you need help

Before calling support or posting for help, have these ready. It speeds everything up.

  • Mail storage before and after
  • Accounts configured
  • Whether trash was emptied
  • Steps already tried

Is Mail trash empty?

Trash holds deleted messages and uses space.

Mail → Empty Trash. Good: trash empty—sort by size next. Bad: already empty—check large messages and attachments.

Yes No

You can change your answer later.

Empty Mail trash

Mail → Empty Trash. Then sort by size to find large messages.

Done

Do you have large messages with attachments?

Attachments use the most space.

View → Sort By → Size. Delete or archive large messages. Good: space freed. Bad: no large messages—archive old mailboxes or rebuild.

Yes No

You can change your answer later.

Archive old mailboxes

File → Export Mailbox. Save to external drive. Delete mailbox from Mail. Or rebuild if Mail is slow.

Done

Is Mail slow or showing errors?

Rebuild can fix corruption.

Mail → Settings → Accounts → Advanced → Rebuild. Or hold Option and open Mail. Good: Mail works. Bad: consider Apple support.

Done

Reviewed by Blackbox Atlas

Frequently asked questions

Why does Mail use so much space?
Trash not emptied, large attachments (PDFs, images), and years of accumulated mail. iCloud Mail also counts toward iCloud storage.
Can I free Mail space without losing important emails?
Yes. Archive important mail to a local folder, then delete or empty trash. Or export mailboxes before deleting.
When should I archive vs delete?
Archive when you want to keep mail but move it off the server. Delete when you do not need the mail at all.

Rate this guide

Was this helpful?

Continue to