Help · Mac storage

How to reduce Mail storage on a Mac.

By Grant and Brad, who make Pangalin's apps · Updated 11 October 2026

Apple Mail keeps a local copy of your messages and the attachments it has downloaded, plus search indexes. For a busy account that's easily several gigabytes. Most of it is also on your mail server, so trimming it is safe, as long as you do it inside Mail.

Never delete files inside ~/Library/Mail in Finder. Your mailboxes and Mail's index live together there, and removing files by hand can corrupt both.

See how much it uses

Choose Apple menu › System Settings › General › Storage and click the ⓘ next to Mail.

1. Erase what's already deleted

Deleted mail and junk can still take space until they're erased.

1. In Mail, choose Mailbox › Erase Deleted Items and pick an account (or all).
2. Choose Mailbox › Erase Junk Mail.

Both are permanent. To have Mail do this automatically, see Mail › Settings › Accounts › Mailbox Behaviors.

2. Find and remove the heaviest messages

3. Select a mailbox and choose View › Sort By › Size.
4. Delete big messages you don't need, or select one and choose Message › Remove Attachments to keep the message but drop its attachments.

Careful: for IMAP accounts (iCloud, Gmail and most others), removing attachments also removes them from the server, permanently. Save any you want first.

3. Clear Mail Downloads

When you open an attachment, Mail saves a working copy in its Mail Downloads folder. The original stays in the message. In Mail › Settings › General, the Remove unedited downloads option controls when Mail tidies these up. By default, Mail removes an attachment you haven't edited when you delete its message.

4. If the store looks far too big

Select a mailbox and choose Mailbox › Rebuild. For IMAP and Exchange accounts, Mail discards its local copies and downloads them again, so the mailbox looks empty for a while. Old Import mailboxes under On My Mac are often left over from moving Macs; delete them in Mail if you don't need them.