Your inbox has been hoarding: reclaiming the gigabytes Mail hides on your Mac

Updated September 2026 · 7 min read

Apple Mail doesn't feel like a storage hog — until you open the storage settings and see it claiming 5, 10, even 20 GB. Most of that isn't the emails themselves; it's the attachments Mail has been quietly downloading and caching for years.

Where Mail stores data on your Mac

Mail keeps everything in ~/Library/Mail. Inside, each email account has its own folder with message files and downloaded attachments. There's also a separate envelope index (a database Mail uses for search).

You don't need to go into these folders directly — Mail gives you built-in tools to manage space. But knowing the location helps when you check what's taking up disk in tools like the Storage settings or Finder's large-file search.

The biggest culprit: downloaded attachments

By default, Mail downloads all attachments for every message in every account. A few years of newsletters with PDF attachments, photo-heavy emails, and large file transfers add up fast.

You can change this behavior:

1. Open Mail → Settings → Accounts.
2. Select an account and click the Account Information tab (or Mailbox Behaviors depending on account type).
3. Look for Download Attachments and change it to Recent or None.

Setting it to "None" means Mail shows a download button on each attachment — you grab only what you need. Emails themselves (the text) still download normally.

Removing attachments from specific messages

If you've already got years of downloaded attachments on disk, changing the setting only affects future messages. For existing ones:

1. In Mail, sort a mailbox by Size (View → Sort By → Size) to find the heaviest messages.
2. Open a message, then go to Message → Remove Attachments from the menu bar.
3. The attachment is removed from the local copy. The email text stays intact.

Emptying the Junk and Trash

This sounds obvious, but Mail often holds months of junk and deleted messages with their attachments still on disk:

• Mailbox → Erase Junk Mail clears the Junk folder for all accounts.
• Mailbox → Erase Deleted Items permanently removes trashed messages.
• In Mail → Settings → Accounts → Mailbox Behaviors, you can set Junk and Trash to auto-erase after 30 days.

Rebuilding the Mail index

Sometimes the Mail envelope index grows disproportionately large (several gigabytes for a moderate inbox). Rebuilding it forces Mail to reindex and usually shrinks the database:

Select a mailbox in Mail's sidebar, then go to Mailbox → Rebuild. This redownloads message headers from the server, so it takes time on large mailboxes — but it's safe and often recovers a few GB.

What not to touch

• Don't delete files inside ~/Library/Mail manually. The database and message files are tightly linked. Removing files by hand corrupts Mail's index.
• Don't delete the envelope index file directly. If it's bloated, use Rebuild instead.
• Don't delete emails you might need. Storage is recoverable; a deleted contract or tax document might not be.

Mail is just one part of the storage puzzle. For caches and system files that pile up alongside it, check our System Data breakdown.

FAQ

Does "Remove Attachments" in Mail delete the file from the server?

For IMAP accounts (Gmail, iCloud, etc.) — yes, it typically removes the attachment from the server copy too. Always save the file locally first if you need to keep it.

How do I stop Mail from downloading all attachments?

Go to Mail → Settings → Accounts, select your account, and set Download Attachments to "Recent" or "None." This only affects future messages — existing downloaded attachments remain on disk until you remove them.

Why does Mail still show large storage after I deleted emails?

Deleted messages go to Trash, which still takes up space. Use Mailbox → Erase Deleted Items to permanently remove them. Also, Mail's search index may need a rebuild (Mailbox → Rebuild) to reclaim space.