MailFundusMac storage full because of Apple Mail? Free up space without losing email
October 2026 · about 4 minutes to read
In short: When your Mac warns that storage is almost full, Apple Mail is often one of the reasons. Mail keeps a local copy of every message and every attachment, and over the years that easily adds up to 10, 20 or more gigabytes. The safest way to free up space is to archive first and clean up afterwards.
Why Mail takes up so much space
Apple Mail stores a copy of every account on your Mac: each message and each attachment. That is convenient, because you can search and read offline. It also means that everything you received over the past ten years sits on your internal drive. With several accounts and large attachments such as PDFs, photos or slide decks, Mail quickly becomes the biggest item on the Mac.
How to see how much space Mail uses
- Quick look: open System Settings > General > Storage. macOS lists how much space Mail uses.
- In detail, in the Finder: choose Go > Go to Folder…, enter ~/Library/Mail, select the folder and choose File > Get Info. “Size” shows what Mail really occupies.
Don’t change anything in that folder by hand. Mail manages it itself, and deleted or moved files can damage mailboxes.
Three ways to free up space
1. Delete old email
The fastest way: select old messages, delete them, empty the Trash. The space is free right away, and the messages are gone for good. That may be fine for personal mail. For business email it usually is not, because many countries require businesses to keep correspondence and invoices for several years.
2. Export mailboxes as .mbox
Mail can export a mailbox as an .mbox file (Mailbox > Export Mailbox…). That is a backup, but hardly a solution: the file is as large as the mailbox, and you can only search it after importing it back into Mail.
3. Archive first, then clean up
The safe way: your email goes into an archive of its own that stays searchable and needs less space. Only once it is certain that everything arrived there completely is Mail cleaned up. You lose nothing and can still find every message.
How MailFundus Archive does it
MailFundus Archive backs up your Apple Mail mailboxes into an archive on your Mac, attachments included, and verifies every message byte for byte. Nothing is moved or deleted without your OK. Only if you choose to, the verified messages go to Mail’s Trash, which you empty yourself.
In the archive you find any message in milliseconds, by sender, subject, text and even by what is inside PDF attachments.
A real example: 76,104 messages from twenty years took up 19.3 GB in Mail. In the archive they take 8.6 GB, with all attachments.
Free for up to 500 messages, with every feature. The full version is US$24.99 once, no subscription (price varies by country).
Free for up to 500 messages: get it on the Mac App StoreBefore you clean up: a current Time Machine backup never hurts, even when you work with an archive. An archive on a single drive is not an archive.