How to reduce Mail storage on a Mac safely

Three different kinds of Mail storage

Mail's messages, attachments and temporary opened-attachment copies are different things. So are space on your Mac and the storage quota at your email provider. A cleanup that helps one may not help the other.

Item	What it contains	What a change can affect
Mail messages and their attachments	Your mailboxes and downloaded message content	Deleting synced mail can affect the server and other devices
Opened-attachment copies	Temporary local copies used when opening attachments	Local storage, separate from removing the attachment from its message
Attachments you saved	Independent files in Downloads or another chosen folder	Your saved file; verify it before deleting any other copy

Open System Settings › General › Storage to assess the Mac's storage. In Mail, Control-click an inbox and choose Get Account Info to inspect account usage. A full online mailbox is not the same problem as a full internal SSD.

Preserve important messages and attachments first

For a mailbox archive, select the mailbox in Mail and choose Mailbox › Export Mailbox. Pick a safe destination. Apple documents export as an .mbox package and import through File › Import Mailboxes.

Save needed attachments using File › Save Attachments, or the attachment control in the message header. Open the saved files to confirm you have what you need. Keep the archive and important saved files on backed-up storage; moving the only copy to another folder on the same full disk isn't an independent backup.

These choices have different purposes. Exporting protects a mailbox you may want to read again; saving an attachment preserves that file. A screenshot of an email is not a replacement for its original spreadsheet or other attached document.

For locally stored “On My Mac” mailboxes, be especially careful about assuming the provider has another copy. Check the actual account and mailbox rather than applying an IMAP assumption to every message.

Start with copies of opened attachments

Apple's Mail › Settings › General › Remove unedited downloads setting controls when temporary attachment copies in Mail Downloads are removed. Choose the option that fits your use. It doesn't remove attachments you deliberately saved elsewhere.

This is different from Message › Remove Attachments. Removing a temporary opened copy does not mean detaching the file from the original message. Keep that distinction when a cleanup tool calls an item a “Mail download.”

If you've edited an attachment, save your work to a deliberate location before clearing temporary copies. Don't rely on a working copy in an app-managed cache as your document archive.

Use supported app settings or a reviewed list for this task. Don't delete the whole ~/Library/Mail folder. It contains mail data, not merely disposable copies of attachments you've opened.

Change what Mail downloads in future

Open Mail › Settings › Accounts, select an account and open Account Information. Review Download Attachments.

Apple's current documentation makes a subtle distinction: Mail always downloads media attachments such as images, PDFs, video and audio. All, Recent and None control other attachment types, such as spreadsheets and ZIP files. Recent covers those types received in the past 15 months.

So “None” does not promise zero attachment storage. Nor should you treat changing a future download preference as a command to erase all previously downloaded content. Recheck the setting for each account you use.

If you often need a document offline, make sure it is actually saved before travelling. A smaller automatic download scope trades local availability for space; it isn't a backup policy.

If you choose to remove message attachments

Save the attachments first. Select the intended message in Mail, then choose Message › Remove Attachments. Apple says the message remains and is marked to show the attachments were removed.

For IMAP, Apple explicitly warns that the attachments are also deleted from the mail server and cannot be retrieved. This is not a “remove download only” command. Other devices using that account cannot be relied on as independent copies after a synced deletion.

Start with a specific message you have reviewed, not a large unexplained selection. If you need the original message to retain its attachment, leave it intact and use the earlier local-copy and download-setting options instead.

Delete unwanted mail deliberately

Apple documents View › Sort By › Size to identify large messages. Review the account, message and attachment before deleting. Mail conversations can include several messages, so inspect the selection rather than assuming you are deleting only the visible reply.

Deleted mail may remain in the account's Trash until permanently erased, depending on mailbox settings. After checking it, Mailbox › Erase Deleted Items lets you choose an account. This permanently removes that deleted mail; it isn't the Finder Trash.

Do not confuse Archive with an independent offline export. Archive usually reorganizes messages within a mailbox system. If your goal is a smaller provider quota, verify the provider's actual storage result after the change.

If the category still seems large, use the System Data guide and the storage guide to inspect other causes. Don't keep deleting wanted messages simply because a category total hasn't changed immediately.

How Tend helps

Tend's Clean Up can list the copies of attachments Mail keeps after you've opened them, only with Full Disk Access enabled. The originals stay in messages. Seeing the list is free; moving reviewed items to the macOS Trash is Pro. Quit Mail and save any attachment edits first. Check the Trash before emptying it.

This scope doesn't include deleting your mailboxes or reducing an email-provider quota. Read Tend's Clean Up help for what the Mail downloads category covers and the permission guide before granting access.

Questions

Can I clear Mail storage without deleting emails?

You can manage temporary copies of opened attachments and reduce future downloads. These are separate from deleting messages or removing their original attachments. Save edited files before clearing working copies.

Does Remove Attachments only delete the Mac download?

No. Apple warns that for IMAP accounts it also deletes the attachments from the mail server and they cannot be retrieved. Save needed files first.

Does Download Attachments: None stop every attachment?

No. Apple says Mail still downloads media such as images, PDFs, video and audio. The setting controls other attachment types, and is not a guarantee that old downloads are removed.

What does Tend clean in Mail?

With Full Disk Access, Tend lists local copies of attachments you have opened. Listing is free; moving reviewed copies to the macOS Trash is Pro. It does not delete your mailboxes or manage your provider’s quota.