How to Clear Apple Mail's Cache and Downloads Folder on Mac

Apple Mail is one of the quietest space hogs on macOS. The app itself is fine, but the mail database — the local copy of every email, attachment, and embedded image you’ve ever received — can balloon to 30GB+ on long-time users with multiple accounts. The Mail Downloads folder is a separate culprit and even fewer people know about it.

Here’s how to find both, and how to clean them up without losing anything important on macOS Sonoma 14 and Sequoia 15.

Where Apple Mail stores everything

Mail’s primary data lives in:

• ~/Library/Mail/V10/ — the mail database (the V10 indicates the Mail version; older Macs may have V9 or V8 too)
• ~/Library/Mail/V10/MailData/ — account settings and signatures
• ~/Library/Containers/com.apple.mail/Data/Library/Mail Downloads/ — the auto-download attachments folder
• ~/Library/Caches/com.apple.mail/ — temporary cache

The mail database itself is ~/Library/Mail/V10/[UUID]/ for each account. Inside, IMAP accounts have INBOX.mbox folders containing every message and attachment.

The Mail Downloads folder is usually the biggest win

Here’s what most people miss: when you click an attachment in Mail to preview it, macOS auto-downloads a copy to a hidden Mail Downloads folder. That copy stays there forever by default.

To see it:

1. Open Finder.
2. Press Cmd+Shift+G.
3. Paste ~/Library/Containers/com.apple.mail/Data/Library/Mail Downloads/.

You’ll find folders for every email you ever previewed an attachment from. PDFs, images, ZIP files, presentations — all duplicated copies of attachments still living in your actual mail.

To clean up:

1. Quit Mail.
2. Select everything in the Mail Downloads folder.
3. Move to Trash.
4. Empty Trash.

You can recover several GB this way on a Mac that’s been around a few years. The originals are still in your email — Mail will re-download on demand if you click the same attachment again.

The mail database: where to be careful

The folder at ~/Library/Mail/V10/ is the actual mail database. Don’t delete it carelessly — it contains every message your Mac knows about.

For IMAP accounts (Gmail, iCloud, Office 365, most modern email), the messages also live on the server, so a local clear forces a redownload but doesn’t lose anything permanently.

For POP accounts or accounts where you’ve deleted server-side messages but kept local copies, deleting the database loses real data.

If you’re sure all your accounts are IMAP and synced:

1. Quit Mail.
2. Move ~/Library/Mail/V10/ to a backup location (or the Trash if you’re confident).
3. Reopen Mail.
4. Mail will rebuild the database by re-downloading from your IMAP servers. This can take a long time — hours for large accounts.

This is the heavy hammer. Most people don’t need it.

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Rebuild a single mailbox to reclaim space

A safer approach: have Mail rebuild specific mailboxes. This re-downloads them from the server and clears local cruft.

1. Open Mail.
2. Click a mailbox in the sidebar.
3. From the menu bar, click Mailbox → Rebuild.
4. Wait for it to finish — can take minutes to hours depending on size.

This often recovers a few hundred MB to a few GB per large mailbox. Works on IMAP accounts.

Clearing Mail’s standard cache

For the disposable cache:

1. Quit Mail.
2. Open Finder, press Cmd+Shift+G.
3. Paste ~/Library/Caches/com.apple.mail/.
4. Move everything inside to the Trash.
5. Empty Trash.
6. Reopen Mail.

This is small (usually under 100MB) but worth grabbing in a thorough clean.

Removing old mail accounts you forgot

If you removed an email account from Mail’s settings but its data folder is still hanging around:

1. Open ~/Library/Mail/V10/.
2. Each account has a folder with a UUID name. Inside is IMAP-[address] or similar.
3. If you see a folder for an account you no longer use, you can move it to Trash.

Heavy-handed, but reclaims real space if you’ve cycled through multiple email accounts.

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Vacuuming the mail envelope index

Mail keeps a SQLite envelope index that tracks message metadata. It can grow inefficient over time. To rebuild it:

1. Quit Mail.
2. Open Terminal.
3. Run: cd ~/Library/Mail/V10/MailData/
4. Run: sqlite3 Envelope\ Index "vacuum;"

This optimizes the database without losing data. Recovers hundreds of MB on large mailboxes. Fully safe — it’s a SQLite optimization command, not a delete.

If sqlite3 isn’t available, you can install it via Homebrew or skip this step. The standard cache clears help plenty without it.

What about Mail rules and signatures?

Those live in ~/Library/Mail/V10/MailData/:

• Signatures/ — email signatures
• RulesActiveState.plist — which rules are on
• SyncedRules.plist — Mail rules

Don’t delete these unless you want to lose signatures and rules. They’re not large anyway.

When Mail itself is slow or buggy

Common Mail problems and fixes:

1. Slow search: Rebuild the envelope index (see above).
2. Account won’t sync: Mail menu → Connection Doctor.
3. Messages stuck in Outbox: Check Activity window (Window → Activity).
4. Mail won’t launch: Hold Shift while launching to open in Safe Mode, then troubleshoot.
5. High CPU usage: Check ~/Library/Mail/V10/MailData/AccountsCache.plist — sometimes corrupt and needs deleting.

A cache clear is a reasonable first thing to try for general sluggishness.

How much space can you actually reclaim?

Realistic numbers from a few real Macs I’ve audited:

• Mail Downloads folder: 1-8GB recovered
• Mail caches: 50-300MB recovered
• Database rebuild: variable, often 1-3GB on heavy accounts
• Removed account residue: depends on history

A typical thorough Mail cleanup recovers 3-10GB on Macs that have been around a few years.

Worth automating?

Mail alone is fine to handle manually — the Mail Downloads folder is the big one and it’s a one-time delete. Doing this across Mail plus every other cache-heavy app on your Mac (browsers, Slack, Discord, Teams, Spotify, Photos, etc.) gets old.

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Bottom line

Apple Mail’s biggest space win is usually the Mail Downloads folder at ~/Library/Containers/com.apple.mail/Data/Library/Mail Downloads/ — duplicate copies of every attachment you’ve ever previewed. Clean that out, optionally rebuild large mailboxes, optionally vacuum the envelope index. None of it touches your actual mail.

Cache: ~/Library/Caches/com.apple.mail/. Database: ~/Library/Mail/V10/. Different beasts, different cleanup approaches.