Mail storage on a Mac is the copy Mail keeps of your email: every message it downloads, the attachments inside them, and spare copies of attachments you've opened. Most of it lives in ~/, and Storage settings shows it as the Mail category. On a Mac with years of email and several accounts, it can reach tens of gigabytes.
The way to shrink it is through Mail, not Finder. Find and delete large messages, remove attachments you've already saved, erase deleted items and junk, then tell Mail to download fewer attachments: Download Attachments set to Recent or None, and Optimize Storage turned on.
Before you delete anything, know what kind of account it's in. In iCloud, IMAP and Exchange accounts, deleting a message or removing an attachment on your Mac also deletes it on the server and on your other devices. In POP accounts and On My Mac mailboxes, the copy on your Mac may be the only one.
One folder is a little different. Mail saves a copy of each attachment you open in a Mail Downloads folder, and copies from messages you keep can pile up there. Those copies come back when you reopen an attachment, so with Mail quit they're usually fine to clear, after you check you didn't edit one in place.
What Mail stores on your Mac
Mail is a local copy of your mail accounts. Even when the originals live on a server, Mail downloads messages so it can show and search them quickly, and work offline. That copy is what takes space.
Where is Mail storage on a Mac?
Mail keeps its data in two places in your Library folder, plus wherever you save attachments yourself.
| Location | What it holds | Who manages it |
|---|---|---|
~/Library/Mail/V10 | Every account's messages and attachments, and On My Mac mailboxes | |
~/Library/Mail/V10/MailData | Mail's own records, such as its index of messages | |
~/Library/Containers/com.apple.mail/Data/Library/Mail Downloads | Copies of attachments you opened from a message | Mail, with your settings |
~/Downloads | Attachments you saved on purpose | You |
~/Library/Metadata/CoreSpotlight | Spotlight's index of content inside apps, mail included | Spotlight |
The V10 folder is named for the version of Mail's data format, and V10 is the one current versions of macOS use. You don't need to open it to manage your mail, and shouldn't change anything inside it.
To look at the Library folder, hold down Option in Finder, choose Go, then Library. Looking is fine. Changing anything in the Mail folder is not, for reasons the rest of this post explains.
What's inside the V10 folder?
Inside ~/ there's a folder for each account, often named with a long identifier rather than the account's name, and one for On My Mac mailboxes. Each holds mailboxes, which hold messages and their attachments as separate files.
Mail keeps an index of all of them in MailData. When files change behind its back, what Mail shows and what's on disk can disagree: Apple notes that a mailbox deleted in Finder may not disappear from Mail. That's why the catalog's Mail messages and attachments entry says to change these files only in Mail.
What is the Mail Downloads folder?
When you open an attachment from a message, Mail saves a temporary copy so another app can open it. Those copies go to ~/, in a subfolder per attachment.
By default, Mail deletes a copy when you delete the message it came from. Copies from messages you keep stay, and so do copies you edited. The originals stay inside your messages, so opening an attachment again simply makes a new copy.
Macworld noted that before OS X Mavericks the folder sat at ~/. If your home folder dates from that era, an old folder there may still hold copies nothing uses.
Why does Mail keep a copy of mail that's on a server?
So it can show messages instantly, search their contents, and let you read them on a plane. iCloud, IMAP and Exchange accounts keep the originals on the mail server, and Mail keeps them in step with it.
Apple's settings pages list no option to keep messages on the server only. The controls Mail offers are over attachments: how many it downloads, and how long it keeps the copies you've opened.
How to see how much space Mail uses
Start with the size, then find out which account and which messages make it up. That tells you whether you have a few huge attachments or simply years of mail.
Mail in Storage settings
Choose Apple menu › System Settings, click General in the sidebar, then click Storage. Apple describes the Mail category as containing emails and attachments. It appears once Mail has stored something.
Storage settings only tells you the total. To act on it, open Mail. Before macOS Ventura, the same figures were under Apple menu › About This Mac › Storage.
Which account uses the most space?
In Mail's sidebar, Control-click an inbox and choose Get Account Info. Apple's Mail guide for macOS 27 points to it for checking an account's storage capacity on the server and how much space each mailbox uses.
It's the quickest way to see whether one account, or one mailbox inside it, holds most of your mail. It might be an old work account, or a shared mailbox you never read.
Where are the largest messages?
Select a mailbox, then choose View › Sort By › Size. The heaviest messages move to the top, usually ones with video, large PDFs or photo sets attached.
Do the same in the Sent mailbox. Every attachment you send is kept there too, so a year of sending photos or presentations adds up on both sides.
To list only messages with attachments, type "attachment" in the search field and choose Message with attachments. Or choose View › Filter and pick a filter that shows only messages with attachments.
Can you check Mail's folders in Finder?
You can open ~/ from the Library folder and choose File › Get Info on it to see its total size. Don't open account folders to delete things, though: Mail can't tell what you removed.
Disk analyzers need Full Disk Access to measure Mail's folders, because macOS keeps Mail's data private. Without it, the folder can look empty or small, and the space goes unexplained.
Why do the numbers differ?
Storage settings, Finder and Get Account Info measure different things. Get Account Info describes the account, including its storage on the mail server, which can hold more mail than your Mac has downloaded. Mailboxes On My Mac aren't on the server at all.
Storage settings measures your Mac, and works out its figures in the background, so they can lag behind.
What kind of account is it?
The type of account decides what deleting means. The same click that frees space safely in one account loses the only copy in another.
iCloud, IMAP and Exchange accounts
These keep the originals on the mail server, and Mail mirrors them. Deleting a message on your Mac deletes it on the server and on every other device that uses the account: your iPhone, webmail, a work PC.
Message › Remove Attachments works the same way. Apple warns that for IMAP accounts, attachments are deleted from the server too and can't be retrieved. iCloud Mail is an IMAP account, so the warning applies to it.
POP accounts
A POP account downloads mail to your Mac and, depending on its settings, removes it from the server afterwards. Mail in a POP account may exist only on this Mac, so treat it like your own files.
On My Mac mailboxes
Mailboxes under On My Mac in the sidebar are local. Apple's guide says you can access them only on the Mac where you created them. If you moved old mail there to make room on a server, this Mac now holds the only copy.
| Where the mail is | Is your Mac's copy the only one? | What deleting on the Mac does |
|---|---|---|
| iCloud account | No, it's on Apple's server | Deletes it everywhere |
| IMAP account, such as Gmail or a work account | No, it's on the provider's server | Deletes it everywhere |
| Exchange account | No, it's on the Exchange server | Deletes it everywhere |
| POP account | Often yes | Deletes the only copy, unless the server kept one |
| On My Mac mailboxes | Yes | Deletes the only copy |
How do you tell which type an account is?
Choose Mail › Settings, click Accounts, and select the account. The settings shown vary with the account type, and a POP account is the one with a setting for removing copies from the server after Mail retrieves them. Server Settings shows the incoming server's host name, which often names the protocol, as in imap or pop.
If you're not sure, open the account's webmail. Mail you can see there is on the server.
- Mail messages and attachments1–365 GB · Review first
- Outlook profiles5–70 GB · Review first
- Messages attachments5–100 GB · Review first
- iPhone and iPad backups10–200 GB · Review first
- Photos library10–500 GB · Managed by macOS
Typical ranges on Macs that have these items at all, from the research behind the app's catalog. The top ends are rare; most Macs sit well below them.
How to reduce mail storage on Mac, step by step
Work from the largest items down. A few dozen messages with video or big PDFs often outweigh thousands of plain ones, so sorting by size comes first.
Delete the messages you don't need
- In Mail, select a mailbox and choose View › Sort By › Size.
- Select messages you don't need. Shift-click to select a range, or Command-click to pick several.
- Click the Delete button in the toolbar, or press Delete. If you selected a conversation, all of its messages are deleted.
- Repeat in Sent, and in any large mailbox Get Account Info pointed to.
Search narrows things down. Type a sender's name, or a date range such as "01/01/20 to 12/31/21", choose the suggestion, then select the results and delete them.
Keep the message, lose the attachment
Often the message matters and the 40 MB video in it doesn't, or you already have the file elsewhere. Remove Attachments keeps the text and drops the files.
- Save any attachment you want to keep first: select the message and choose File › Save Attachments, or drag the attachment to a folder.
- Select the message, or several messages.
- Choose Message › Remove Attachments.
The message stays in its mailbox with a note that its attachments were removed. In an iCloud or IMAP account, the attachments are gone from the server too, with no way to get them back, so the first step isn't optional.
Erase deleted items
A deleted message goes to the account's Trash mailbox, and it still takes space there, on your Mac and on the server. Choose Mailbox › Erase Deleted Items, then choose an account or all of them. Or Control-click a Trash mailbox in the sidebar and choose Erase Deleted Items.
Erasing is permanent. Look through the Trash mailbox first and drag back anything you deleted by mistake.
Erase junk mail
Junk mail is easy to forget because you never open it. Choose Mailbox › Erase Junk Mail, which Apple lists among its own steps for freeing storage space on a Mac.
Delete a mailbox you no longer need
Select the mailbox in the sidebar and choose Mailbox › Delete Mailbox. Apple's warning is plain: it permanently deletes the mailbox and everything in it, including mailboxes inside it, and can't be undone.
Use this for things like an old project folder or a mailing list archive, and only after checking nothing in it matters. Never delete a mailbox in Finder: Apple notes the change may not appear in Mail.
Does deleting email free space straight away?
Not always. The messages stay until you erase deleted items, and Storage settings updates its figures in the background. If you use Time Machine, a local snapshot may also hold on to the deleted files for a while.
Give it time, and check again later before deciding it didn't work.
Stop Mail from downloading so much
Deleting is a one-off. These settings change what Mail keeps from now on, so the space doesn't fill up again.
Download Attachments: All, Recent or None
Choose Mail › Settings, click Accounts, select an account, then click Account Information. The Download Attachments menu has three choices:
- All: Mail always downloads attachments.
- Recent: Mail downloads only attachments received within the past 15 months.
- None: Mail doesn't download any of these attachments. In a server account, they stay in the message on the server.
There's a catch Apple spells out. Mail always downloads media attachments, such as images, PDFs, video and audio files. The setting only covers the other kinds, such as spreadsheets and zipped files. So None helps most in accounts full of documents and archives, and less in one full of photos.
Set it for each account. A work account full of shared spreadsheets and an old account you rarely read are both good candidates for Recent or None.
Optimize Storage
Choose Apple menu › System Settings, click General, then Storage, and turn on Optimize Storage. For Mail, Apple says it keeps only recent email attachments on your Mac when storage space is needed. It also removes Apple TV movies and shows you've already watched.
The attachments stay in your messages on the server, and Mail downloads one again when you open it. For POP mail and On My Mac mailboxes there's no server copy to fall back on, so keep that in mind if most of your mail is local.
Remove unedited downloads
Choose Mail › Settings, click General, and find Remove unedited downloads. It sets when Mail deletes the copies in the Mail Downloads folder. By default, a copy you haven't edited or saved goes when you delete the message that contains it.
Choose an earlier point if you open many attachments from messages you keep. Mail doesn't delete attachments you've saved, so files in your Downloads folder aren't affected.
Erase deleted and junk messages automatically
Choose Mail › Settings, click Accounts, select an account, then click Mailbox Behaviors. Two menus there save you from erasing by hand: Erase deleted messages and Erase junk messages.
Apple suggests a setting other than Never for both, to keep the account under its provider's storage limit. Pick a delay that still gives you time to recover something deleted by mistake.
| Setting | Where it is | What it changes |
|---|---|---|
| Download Attachments | Mail › Settings › Accounts › Account Information | Whether non-media attachments download: All, Recent or None |
| Optimize Storage | System Settings › General › Storage | Keeps only recent attachments on the Mac when space is needed |
| Remove unedited downloads | Mail › Settings › General | When Mail clears copies of attachments you opened |
| Erase deleted messages | Mail › Settings › Accounts › Mailbox Behaviors | When the Trash mailbox is emptied |
| Erase junk messages | Mail › Settings › Accounts › Mailbox Behaviors | When the Junk mailbox is emptied |
| Remove copy from server | Mail › Settings › Accounts › Advanced, POP only | How long a POP server keeps mail after it downloads |
Where these settings were in older versions
Before macOS Ventura, Mail's settings were called Preferences: Mail › Preferences instead of Mail › Settings. Storage settings itself was under About This Mac, as a Storage tab.
On macOS 26 Tahoe and macOS 27, the Mail guide describes the same settings in the same places. The macOS 27 guide adds the tip about Get Account Info for checking an account's storage.
The Mail Downloads folder
This is the one part of Mail's storage that's reasonable to clear in Finder, with care. The catalog rates it Usually safe: unedited copies come back when you reopen an attachment, but an edited one might be the only version.
Is it safe to delete the Mail Downloads folder?
Mostly, yes. Unedited copies are saved again the next time you open an attachment, because the original stays in the message. Quit Mail first, so it isn't using a copy while you move it.
The exception is an attachment you opened from Mail, edited and saved in place. Macworld found that some apps save over the copy in Mail Downloads, so your edited version may exist only there. If you've ever worked that way, look before you remove.
How do you clear Mail Downloads in Finder?
- Quit Mail.
- In Finder, choose Go › Go to Folder, enter
~/, and press Return.Library/ Containers/ com.apple.mail/ Data/ Library/ Mail Downloads - Choose View › as List and sort by Date Modified. Open anything recently changed to check it isn't an edited file you want to keep, and save those elsewhere.
- Select the subfolders inside and move them to the Trash.
- Open Mail and check an attachment or two still opens. Then empty the Trash.
Finder may show the container under the app's name, Mail, rather than com.apple.mail. The containers and group containers post explains why some containers appear more than once.
How big does it get?
It depends on how you work. Someone who opens attachments by double-clicking, keeps the messages, and never deletes them can collect years of copies. Someone who saves attachments with Save Attachments and deletes messages afterwards may have almost nothing there.
Clearing it once and then setting Remove unedited downloads keeps it from building up again.
Saved attachments are yours
Attachments you saved, whether with Save Attachments, Save All or by dragging, go to your Downloads folder unless you chose another folder in Mail › Settings › General. They're ordinary files. Mail doesn't track them, so it's up to you to clear them.
The guide to finding large files covers sorting Downloads and deciding what to keep.
Keep old mail without keeping it on the Mac
Some mail is worth keeping but not worth carrying. Archives from a job you left, a closed business account, or ten years of family email can move off your startup disk without being lost.
Export a mailbox to an external drive
- Select one or more mailboxes in Mail's sidebar.
- Choose Mailbox › Export Mailbox.
- Choose a folder on an external drive, or create one, then click Choose.
Mail saves each mailbox as an .mbox package. It never overwrites an earlier export; it makes a new one with a number added. To read the mail again later, choose File › Import Mailboxes and select Apple Mail; the messages arrive in a mailbox called Import.
Exporting doesn't remove anything by itself. Check an export before you delete the originals: import it, look through the Import mailbox, then delete the Import mailbox.
Save important messages as PDFs
For a handful of messages you need as records, such as receipts, contracts or letters, select them and choose File › Export as PDF. File › Save As saves Rich Text, Plain Text or the raw message source.
PDFs open anywhere without Mail, which makes them a good format for anything you might need in ten years.
Remove an account you no longer use
When you remove an account in Mail, its messages are removed from your Mac. Copies stay on the account's mail server, available through webmail. For an old account that still works online, this can free its whole share of Mail's storage at once.
- If you're not sure everything is on the server, move or copy what you want to keep into a mailbox On My Mac first, as Apple suggests.
- Choose Mail › Settings, click Accounts, select the account, and click the minus button.
- If the account is also used by other apps, Mail sends you to System Settings › Internet Accounts. Select the account there and turn Mail off.
Be careful with POP accounts. Their mail may already have been removed from the server, so removing the account can remove the only copy. Export its mailboxes first.
Turning an account off isn't the same
Deselecting Enable this account in Account Information takes the account offline: its mailboxes and messages no longer appear in Mail. Apple doesn't say it frees space, so treat it as a way to pause an account, not to shrink Mail's storage.
What not to do
Most advice about Mail storage is about making space quickly. The quick routes tend to damage the mailbox or lose mail you meant to keep.
Don't delete files in the Mail folder
Moving account folders, mailbox folders or message files from ~/ to the Trash leaves Mail's index pointing at files that aren't there. Messages can look missing or garbled, and in server accounts Mail may download them again, taking the space straight back.
The same goes for MailData. It holds Mail's records, not your mail, so removing it frees little and leaves Mail to rebuild them.
Is Rebuild a way to free space?
No. Mailbox › Rebuild is a repair for messages that look missing or garbled, or a search that doesn't find what it should. Apple's earlier Mail guides warned that rebuilding an IMAP or Exchange mailbox discards the copy on your Mac and downloads it again, which leaves the mailbox empty until it's done.
Rebuild a mailbox when it's broken, not when your disk is full.
Don't remove an account to "reset" Mail without checking
Removing and adding an account back is often suggested as a way to clear Mail's storage. It works only for mail that's still on the server. Mail that exists only on your Mac, as in many POP accounts, isn't coming back.
Don't clear Mail's preferences or saved state
Mail's preferences and saved window state are tiny. Removing them frees nothing worth having and resets how Mail behaves. They aren't caches.
Don't paste Terminal commands to clear Mail
Some guides suggest a command to delete Mail's folders or downloads. Commands that delete files can't be undone and don't care which files are the only copies. Everything in this post works through Mail, Finder and System Settings.
| Don't | Why | Instead |
|---|---|---|
Delete folders inside ~/Library/Mail | Mail's index breaks, and server mail may download again | Delete messages in Mail |
Delete MailData | It's Mail's records, which Mail has to rebuild | Leave it |
| Use Rebuild to save space | It's a repair, and can download the mailbox again | Rebuild only a broken mailbox |
| Remove a POP account without exporting | Its mail may exist only on the Mac | Export its mailboxes first |
| Remove attachments before saving them | In IMAP accounts they're gone from the server too | Save, then remove |
| Clear Mail's preferences | They're tiny, and settings reset | Leave them |
Other mail apps on a Mac
Mail isn't the only app that keeps a local copy of your email, and the same rules apply to the others: manage the mail in the app, never in its folder.
Outlook for Mac
Outlook keeps each profile's mail, attachments, calendars and contacts in Office's group container. The catalog's Outlook for Mac profiles entry rates it Review first: mail in Microsoft 365, Exchange and IMAP accounts stays on the server too, but items in On My Computer folders are stored only on your Mac.
To shrink it, delete mail you don't need in Outlook and empty Deleted Items. To drop an account you no longer use, choose Tools › Accounts, select it, and choose Manage › Remove Account.
Webmail in a browser
If you read Gmail or Outlook.com only in a browser, your mail stays on the server, and the browser keeps only its usual cache and site data. That's the browser's storage, cleared in its own settings.
Spotlight's index of your mail
Spotlight keeps an index of content inside apps, including Mail, in ~/. The catalog rates it Managed by macOS: Spotlight maintains it, and removing it only makes searches in Mail find less until it's rebuilt.
Keep Mail from filling up again
Mail grows a little with every message, which is fine. The aim is to stop it collecting things you'll never open again.
A short routine
- Every few months, sort Inbox and Sent by size and deal with the top few dozen messages.
- Let Erase deleted messages and Erase junk messages run on a schedule rather than Never.
- Set Download Attachments to Recent or None in accounts you rarely read.
- Save attachments you need with Save Attachments, file them, then remove them from the message if it's large.
- Once a year, export finished mailboxes to an external drive and remove what you exported.
A worked example
Say Storage settings shows a large Mail category on a laptop with an iCloud account, a work IMAP account and an old POP account from a previous internet provider.
Get Account Info shows the iCloud account holds most of it, in Sent and in a mailbox of old newsletters. Sorting Sent by size turns up a run of messages with video attached. Saving the videos to an external drive and choosing Remove Attachments shrinks them, on the Mac and in iCloud.
The newsletter mailbox goes with Mailbox › Delete Mailbox after a last look. The POP account's mail gets exported to the drive before the account is removed. Download Attachments set to None in the work account, and Optimize Storage turned on, keep it smaller from then on.
How much space should Mail take?
There's no right figure. Ten years of plain email takes surprisingly little; a single year of sending photos and video can take far more. What matters is whether the largest messages are ones you still need, and whether this Mac is the only place they exist.
Does a smaller mailbox make Mail faster?
Freeing space doesn't make a Mac faster, and Apple doesn't say a smaller mailbox speeds Mail up. Apple suggests keeping mailboxes from getting too big so you can find messages, and organizing mail into mailboxes or with rules. Messages are the other Apple app that collects attachments, and the same approach works there.
How the app does it
Wombit is a native Mac app that shows what's using your storage and explains every item in plain language. It scans the whole disk or any folder, reading only names, sizes and dates. File names and paths never leave your Mac.
Mail's two folders and Outlook's profiles appear on the map with their real sizes, each explained from its catalog entry:
~/
Library/ Mail/ V* The messages, attachments and mailboxes Mail keeps on this Mac for all your email accounts.
Review first · Explained only: the app shows you how
~/
Library/ Containers/ com.apple.mail/ Data/ Library/ Mail Downloads Copies of email attachments that Mail saves here when you open them from a message.
Usually safe · Moves it to the Trash
~/
Library/ Group Containers/ UBF8T346G9.Office/ Outlook/ Outlook 15 Profiles Outlook's local copy of your mail, attachments, calendars and contacts, in a folder for each profile.
Review first · Explained only: the app shows you how
Mail's mailboxes are Review first. The app doesn't move them or anything inside them; it explains what the folder holds, warns that deleting in a server account deletes everywhere, and points you to Mail's own steps. Outlook's profiles get the same treatment, with Outlook's steps.
Mail Downloads is Usually safe, so it never starts checked. It's listed in Apple Data, where you choose Mail downloads one by one, and anything you move goes to the Trash first, where Undo and Put Back work.
macOS keeps Mail's data private until you allow an app to read it. With Full Disk Access, the scan measures it; without it, the app lists Mail's folders as ones it couldn't read rather than guessing.
The scan, the map, the explanations, System Data explained and Apple Data are free. Cleanup and the Apple Data actions are PRO: one payment of $4.99 with lifetime access. Every Pro tool's review is free to open, so you see what would go and why before you buy.
Frequently asked questions
Where are Mail attachments stored on a Mac?
Attachments you receive are stored with their messages in ~/Library/Mail, in a folder for each account. Copies of attachments you opened go to the Mail Downloads folder in Mail's container, and attachments you save on purpose go to your Downloads folder unless you chose another one in Mail's General settings.
Why is Mail using so much storage on my Mac?
Mail downloads a copy of every message and, by default, every attachment, for every account. Years of mail, sent attachments, a full Trash or Junk mailbox and copies in Mail Downloads all add up. Control-click an inbox and choose Get Account Info, then sort mailboxes by size to see where it comes from.
Does deleting emails on my Mac delete them from iCloud and my iPhone?
Yes, in iCloud, IMAP and Exchange accounts. Mail mirrors the server, so a message you delete on the Mac is deleted on the server and on every device that uses the account. Removing attachments from an iCloud or IMAP message deletes them from the server too.
How do I stop Mail from downloading attachments on a Mac?
Choose Mail › Settings, click Accounts, select an account, click Account Information, and set Download Attachments to Recent or None. Mail still downloads media attachments such as images, PDFs, video and audio; the setting covers other kinds, such as spreadsheets and zipped files.
Can I delete the Mail folder in my Library?
No. It holds your messages and Mail's index of them, and mail in POP accounts or On My Mac mailboxes may exist nowhere else. Deleting files there leaves Mail out of step with its own data. Delete messages and attachments in Mail instead.
Does Optimize Storage delete my emails?
No. For Mail, Optimize Storage keeps only recent email attachments on your Mac when space is needed. The messages stay, and an attachment downloads again from the server when you open it.
Can I move Mail's storage to an external drive?
Apple doesn't document a way to move Mail's data folder. To keep old mail off your startup disk, select the mailboxes and choose Mailbox › Export Mailbox, save the .mbox packages to the drive, check them, then delete the originals in Mail. File › Import Mailboxes brings them back.
Sources
- Delete emails and manage storage in Mail on Mac · Apple
- Change Account Information settings in Mail on Mac · Apple
- View, save, or delete email attachments in Mail on Mac · Apple
- Change General settings in Mail on Mac · Apple
- Optimize storage space on your Mac · Apple
- Solving the mysteries of the Mail Downloads folder · Macworld