How to Delete Mail Attachments and Downloads on Mac

How Apple Mail Stores Attachments

When you use the built-in Mail app on macOS, it downloads and caches attachments locally so you can open them instantly without waiting for a re-download. For most IMAP and Exchange accounts, Mail keeps a local copy of message bodies and attachments in a hidden database inside your Library folder. The main location is ~/Library/Mail, and within it you will find a versioned folder such as ~/Library/Mail/V10 (the version number changes between macOS releases).

Inside that folder, each account and mailbox has its own structure, and attachments are stored in Attachments and Data sub-folders scattered throughout. Because Mail caches everything by default, a mailbox with years of newsletters, PDFs, screenshots, and the occasional large video can occupy a surprising amount of space — often several gigabytes and sometimes tens of gigabytes on heavy email users.

Why Mail Storage Balloons Over Time

The reason Mail grows so large is that its default behaviour errs heavily toward keeping everything. A few factors compound the problem:

• Full local caching. By default, many account types download all messages and attachments for offline access, so every attachment you have ever received is mirrored to disk.
• No automatic pruning. Mail does not remove old cached attachments on its own. A 40 MB presentation from four years ago stays on disk indefinitely.
• Multiple accounts. If you have work, personal, and iCloud accounts all configured in Mail, each maintains its own cache, multiplying the footprint.
• Sent attachments count too. Files you attached to outgoing messages are cached alongside received ones.
• The Envelope Index. Mail maintains a large search database (Envelope Index) that can itself grow substantial and occasionally becomes bloated or corrupt.

All of this contributes to the mysterious "System Data" or "Other" storage category in About This Mac, which is often where Mail's cache silently hides.

How to Delete Attachments from Within Mail (Safest Method)

The safest way to reclaim space is to let Mail itself remove the attachment downloads. This clears the local copies while keeping the emails intact — the messages stay in your mailbox, just without the cached attachment on your Mac. Mail re-downloads an attachment the moment you open that message again.

1. 1
   Open Mail and find large emails. Use the search field or sort a mailbox by size if your view supports it. Newsletters and threads with big PDFs or images are the best targets.
2. 2
   Select a message with attachments. Click the email in the message list so it is highlighted. You can Command-click to select several at once.
3. 3
   Remove the attachment. In the menu bar, choose Message > Remove Attachments. Mail strips the cached attachment from the local copy while keeping the message text. The message shows a note that the attachment was removed.
4. 4
   Repeat across mailboxes. Work through your largest mailboxes — All Inboxes, Sent, and any archive folders — removing attachments from old threads you no longer need offline.
5. 5
   Confirm the space is freed. Space is released as Mail updates its local store. Quitting and reopening Mail helps it compact the database and finalise the reclaimed space.

Stop Mail from Caching Everything

You can prevent the cache from rebuilding by changing how much Mail stores locally. This is the single most effective long-term fix.

Open Mail > Settings (or press Command + Comma), go to the Accounts tab, select an account, and open the Account Information section. Look for the Download Attachments option and change it from All to Recent or None. With "None," Mail keeps message text locally but fetches attachments only when you open them. With "Recent," it keeps only recent ones. Repeat for each account. This dramatically slows how fast the local cache grows without affecting anything on the server.

Rebuild the Mailbox to Reclaim Space

If Mail's local store has become bloated, rebuilding a mailbox forces Mail to discard its local cache for that mailbox and re-sync a clean copy from the server. Select a mailbox in the sidebar, then choose Mailbox > Rebuild from the menu bar. Mail clears the local data and re-downloads message headers, keeping attachments only per your download setting. This is especially useful when the Envelope Index has grown corrupt or oversized.

Because rebuilding re-fetches data from the server, only do this for accounts that are fully server-backed (IMAP, Exchange, iCloud). For POP accounts, where mail may exist only on your Mac, avoid rebuilding or deleting the local store, as those messages may not exist anywhere else.

Clear Mail Attachments Automatically with TrimyMac

Navigating ~/Library/Mail by hand is risky — the folder structure is dense and it is easy to delete the wrong thing. TrimyMac's Smart Clean recognises Mail's cached attachment and download locations, calculates how much reclaimable space they hold, and clears only the safe cache copies while leaving your actual mail store and message database untouched. You get the space back without ever opening a hidden Library folder.

1. 1
   Download and open TrimyMac. Install it from the link below and launch it from your Applications folder.
2. 2
   Run Smart Clean. Click Smart Clean on the home screen. TrimyMac scans your disk, including Mail's cached downloads and attachments.
3. 3
   Review the Mail category. Expand the results to see how much space Mail's cached attachments occupy, shown separately from other categories.
4. 4
   Select and clean. Tick the Mail attachments category and click Clean. Your emails stay put; only the reclaimable local copies are removed.

Is It Safe to Delete Mail Attachments?

For server-backed accounts — iCloud, Gmail via IMAP, Outlook/Exchange, and most work email — yes, it is completely safe. The attachments you clear locally are cached copies; the originals remain on the mail server and download again the instant you open the message. Nothing is permanently lost. Using Mail's own "Remove Attachments" command or a tool that targets only the cache is the safest route because it respects Mail's database structure.

The one exception is POP accounts, which sometimes store the only copy of a message on your Mac. If any of your accounts are POP, be conservative: use "Remove Attachments" on individual messages you are sure you no longer need offline, and avoid bulk-deleting the local Mail store for those accounts. When in doubt, check the account type under Mail > Settings > Accounts before clearing anything.