Why Apple Mail is taking up so much space on your Mac
Apple Mail taking up space on your Mac? It keeps a local copy of every message and every attachment. Here's where it stores them and how to shrink it safely.
If Mail is taking up space on your Mac, showing up as a fat "Mail" slice in Storage or quietly padding out "System Data", it's usually doing exactly what it was built to do. Apple Mail downloads and keeps a local copy of every message you receive, and, depending on your settings, every attachment along with it. The messages are small. The attachments are not.
Why Mail is taking up so much space on your Mac
Mail is an offline-first client. It syncs your mailboxes down to disk so you can read, search, and reply without a connection. Each message is a small .emlx file; plain text is cheap. The weight comes from attachments: PDFs, image galleries, the 40 MB video someone dropped into a thread, years of newsletter graphics. By default Mail downloads all of them and holds onto them locally. Multiply that across every account and every year, and Mail's local store climbs into many gigabytes.
Deleted and junk mail count too, until you actually erase them (more on that below). All of this shows up under Mail in System Settings → General → Storage, and some of it (caches and container data) lands in the System Data catch-all rather than under Mail's own label.
Where Mail keeps all of it
Two locations matter, and which one holds what depends on your macOS version:
~/Library/Mail: the main store. Inside is a version-numbered folder (V10on Ventura through Sequoia, lower numbers on older releases) holding your accounts, mailboxes, the.emlxmessages, and their downloaded attachments.~/Library/Containers/com.apple.mail/…: on recent, sandboxed macOS, Mail also keeps data here, including the Mail Downloads folder at~/Library/Containers/com.apple.mail/Data/Library/Mail Downloads/, where attachments you've opened or previewed get saved.
The exact folders shift between macOS releases, so open these and see what's actually there before you delete anything; don't assume. ~/Library is hidden by default: in Finder, open the Go menu, hold Option, and Library appears in the list.
How to shrink Mail's footprint (start in the GUI)
Ordered safest first.
1. Stop downloading every attachment. Open Mail → Settings → Accounts, pick the account, click Account Information, and find Download Attachments. Three options:
- All: Mail keeps a local copy of everything. This is the default, and the reason the folder is so big.
- Recent: only attachments received within roughly the last 15 months (Apple's definition).
- None: Mail keeps no local copies at all.
Set it to Recent or None for an IMAP account. This is the non-destructive lever: the attachments stay on the mail server, and Mail downloads them on demand when you open a message. It just stops Mail from hoarding a local copy of every one. It won't shrink the folder instantly, but it stops the bleeding.
2. Remove attachments from messages you already have. Select a message (or several), then choose Message → Remove Attachments. In Apple's words, "The message remains in the mailbox and is annotated to indicate that all attachments were manually removed." You keep the email and its text; you drop the heavy files.
The honest caveat is that this is not the reversible option. Apple states plainly that "for IMAP accounts, attachments are also deleted from the mail server and can't be retrieved." So for IMAP, removing an attachment this way is permanent: gone locally and on the server. If there's any chance you'll want the file, save it out of Mail first, or use the Download Attachments setting above instead. For the wider question of what's genuinely safe to remove, see what you can safely delete on Mac.
3. Empty Mail's Trash and Junk. Deleting a message just moves it to Mail's own Trash, where it still occupies local space until it's erased. In Mail, use Mailbox → Erase Deleted Items (choose the account) and Mailbox → Erase Junk Mail. Attachments sitting in junk and deleted mail are a common quiet hog.
4. Clear the Mail Downloads folder. Attachments you open get copied into the Mail Downloads folder and are never cleaned up. With Mail closed, open ~/Library/Containers/com.apple.mail/Data/Library/Mail Downloads/ and empty it. These are duplicates of files still attached to your messages (or already saved elsewhere), so clearing them doesn't touch your actual email; it's the same kind of disposable app data covered in clearing app caches on Mac.
The short version
Mail is big because it stores a local copy of every message and, by default, every attachment, and the attachments are the weight. Point Download Attachments at Recent or None, strip attachments off old messages (remembering that IMAP deletes them server-side too), empty Mail's Trash and Junk, and clear the Mail Downloads folder. Mail is only one line on a longer list, though; if the disk is genuinely full, work through the ranked way to free up space on Mac, where Photos, video, and old iOS backups usually dwarf it.
Doing this by hand means unhiding ~/Library, telling the version-numbered Mail store apart from the sandboxed container, and knowing which "remove attachment" click is reversible and which one wipes the server copy. Plumby surfaces big forgotten stores like Mail's local attachment pile, shows you the exact path and measured size before it moves anything, and acts only on your command. It never touches your documents, photos, or projects.
