If your Mac's storage is creeping toward full and you use Apple Mail, the culprit may be sitting in a folder you've never opened. Mail quietly accumulates attachment previews, cached remote content, and copies of every file you've ever opened from an email — and none of it appears in the obvious places. This guide shows you exactly where those files live, how to clear mail downloads on Mac without losing a single email, and which locations are safe to wipe versus which ones you should leave alone.
Where Are Mail Attachments Stored on Mac?
Apple Mail stores attachment-related data in two distinct locations, and understanding both is the key to cleaning them up safely.
1. The Mail Downloads Folder
When you open an attachment by clicking it inside Mail — but don't explicitly save it to a location like your Desktop or Documents — macOS drops a copy here:
~/Library/Containers/com.apple.mail/Data/Library/Mail Downloads/This is the mail downloads folder on Mac. It is sandboxed inside Mail's container, which is why it does not appear under your main ~/Downloads folder. Files here are working copies. If you saved an important attachment to your Desktop or another folder, the file in Mail Downloads is a duplicate — deleting it does not remove the version you explicitly saved.
2. The Mail Message Attachment Cache
Mail also stores inline attachments and embedded images alongside each message in its main data store:
~/Library/Mail/V10/Inside each account's folder you will find .mbox bundles, and within those, Attachments/ subdirectories. These are the actual attachment bodies Mail has downloaded from your mail server for offline access. On IMAP accounts, these files can be re-fetched from the server if you delete them — but there is nuance here that matters (see the safety section below).
3. Remote Content URL Cache
Mail caches remote images (email newsletters, tracking pixels, inline graphics) in:
~/Library/Mail/V10/MailData/RemoteContentURLCacheThis is pure cache and is always safe to delete.
How Much Space Can You Reclaim?
It varies enormously by usage. A busy inbox over several years can accumulate gigabytes in attachment data. The ~/Library/Mail/ folder as a whole is often 2–10 GB on an active machine. The Mail Downloads folder is usually smaller (under a few hundred MB) unless you regularly open large files from email without saving them.
To check your own sizes, open Terminal and run:
du -sh ~/Library/Mail/
du -sh ~/Library/Containers/com.apple.mail/Data/Library/Mail\ Downloads/Step-by-Step: Clear the Mail Downloads Folder
This is the safest cleanup and the most straightforward place to start.
- Quit Mail completely. Press Command-Q or choose Mail > Quit Mail. Do not skip this step — Mail can re-create files or lock the folder while running.
- Open Finder. In the menu bar choose Go > Go to Folder (or press Shift-Command-G).
- Paste this path and press Return:
~/Library/Containers/com.apple.mail/Data/Library/Mail Downloads - Select all files with Command-A and move them to the Trash with Command-Delete.
- Empty the Trash. Right-click the Trash icon and choose Empty Trash.
- Relaunch Mail. Your emails, attachments within messages, and all account data are untouched.
This clears all the working copies Mail stashed when you opened attachments. You will not lose access to any attachment that is still on the server — just click the attachment in the email again and Mail will re-download it.
Step-by-Step: Delete Mail App Attachments to Free Space (Cached Message Bodies)
Clearing the attachment bodies that Mail downloaded for offline reading requires more care. The right way to do this is through Mail itself, not the file system directly.
Using Mail's Built-In "Remove Attachments" Feature
- In Mail, select one or more messages that contain large attachments you no longer need locally.
- Choose Message > Remove Attachments from the menu bar.
- Mail deletes the local attachment body. For IMAP accounts, the attachment still exists on the server and can be re-downloaded by clicking it again.
This is the Apple-supported method and the one least likely to cause problems.
Clearing the Remote Content Cache via Terminal
The remote image cache is always safe to delete manually. With Mail closed, run:
rm -rf ~/Library/Mail/V10/MailData/RemoteContentURLCache/*Mail will rebuild this cache as needed the next time you open messages with remote images.
What Is Safe to Delete — and What Is Not
| Location | Safe to delete? | Notes |
|---|---|---|
Mail Downloads/ |
Yes | Working copies only. Originals remain on the server. |
MailData/RemoteContentURLCache |
Yes | Pure cache. Rebuilt automatically. |
Attachment bodies inside .mbox bundles |
Yes, via Mail's Remove Attachments menu item | IMAP only: the attachment remains on the server. POP accounts: the server copy may be gone — verify before deleting. |
~/Library/Mail/V10/MailData/Envelope Index |
No | Mail's message database. Deleting it forces a full rebuild and can cause message loss if interrupted. |
.emlx files (message bodies) |
No — use Mail to delete messages | Deleting these directly can corrupt your mailbox index. |
~/Library/Mail/V10/ (entire folder) |
No | This is your entire local mail store. Deleting it removes all locally cached messages. |
Important: Cleaning is permanent once you empty the Trash. If you use a POP3 email account (less common today, but still used), attachments may not be re-downloadable from the server after you delete them locally. When in doubt, check whether your account type is IMAP or POP3 in Mail > Settings > Accounts.
The Faster Route: Let Crumb Surface It
If you would rather not navigate the Library manually, Crumb handles the discovery step automatically. Its whole-Mac audit walks every user folder and flags large or stale caches — including the Mail Downloads folder — with plain-English descriptions. For each item it shows what the folder is, how large it is, and whether it is safe to remove. You can then clear it with one click instead of copying paths into Finder's Go to Folder dialog.
Crumb's "Is this safe to delete?" AI is also useful if you stumble onto an unfamiliar path inside the Mail container and want a quick explanation before you act.
How to Find and Open the Mail Downloads Folder Quickly
For future reference, here are three ways to get back to the mail downloads folder on Mac without memorizing the full path:
- Finder Go to Folder: Shift-Command-G, then paste
~/Library/Containers/com.apple.mail/Data/Library/Mail Downloads - Terminal:
open ~/Library/Containers/com.apple.mail/Data/Library/Mail\ Downloads - Spotlight shortcut: Mail does not expose this folder via Spotlight, so the above methods are more reliable than searching.
Preventing Attachment Buildup Going Forward
- Save attachments you need to a real folder (Documents, iCloud Drive, etc.) instead of only opening them from within Mail. That way you control where the file lives and Mail Downloads stays clean.
- Turn off "Load remote content in messages" in Mail > Settings > Privacy if you don't need inline images. This keeps the RemoteContentURLCache from growing.
- Delete large email threads you no longer need. Inbox maintenance is the most reliable way to keep your Mail folder small over time.
- Run a periodic audit — quarterly is usually enough for most users — to catch any large caches before they compound.
Conclusion
The Mail app hides its footprint well: there is no obvious "Mail cache" entry in macOS Settings, and the Mail Downloads folder sits three levels deep inside a sandboxed container most users never open. The good news is that clearing these files is straightforward once you know where to look, and it carries no risk of losing emails or attachments that still live on your mail server. Start with the Mail Downloads folder — it is always safe to wipe — and use Mail's built-in Remove Attachments feature for anything inside the message store itself. If you want to download Crumb and let it find these folders for you during a full-disk audit, that works too; but the manual steps above will get you the same result.