Large attachments quietly pile up over time, and Mail keeps local copies so you can read messages offline. The good news is that you can clean this up in minutes and set a few habits so it does not happen again.
In this post we will show you how to see what is using space, remove unneeded attachments, and adjust a setting so fewer files are stored on your Mac.
How to check storage and find out if Mail is really the culprit
- Open System Settings. Click the Apple menu, choose System Settings, select General, then Storage.
- Look at the categories. You will see how much space each category uses, including Mail. This view updates as you free space.
Tip: If Mail is consuming a lot of space, attachments are usually to blame. We will tackle those next.
Remove space-hogging attachments, keep the emails
You can keep your messages and delete only the attachment files saved on your Mac.
- Open Mail.
- Select one or more messages that have paperclip icons.
- Choose Message > Remove Attachments.
- The emails stay, only the attachments are removed from local storage.
- For IMAP accounts, removing attachments also removes them from the mail server, so first save anything important to a folder on your Mac via File > Save Attachments or the Attach button.
Quick helper: To find the biggest emails first, choose View > Sort By > Size in Mail, then remove attachments from the top of the list.
Set Mail to download fewer attachments automatically
Future-proof your storage by telling Mail to keep only recent or no attachments locally. You can still open any attachment on demand, it will just fetch it when needed.
- In Mail, go to Mail > Settings > Accounts.
- Select the account, open Account Information.
- Next to Download Attachments, choose Recent or None.
- Recent keeps attachments from roughly the last 15 months.
- None avoids automatic downloads. You can still click to fetch a specific file later.
Another system-wide helper: In System Settings > General > Storage, turn on the recommendation to keep only recent email attachments when space is needed. This works alongside the Mail setting above.
Optional tidy-up: Rebuild a mailbox
If Mail’s local storage still looks large after cleanup, you can ask Mail to “refresh a mailbox”. This discards local copies on your Mac, then re-downloads what is needed from the server. Your messages may appear to vanish while rebuilding, then return as Mail finishes.
- In Mail, select a mailbox in the sidebar.
- Choose Mailbox > Rebuild.
This can take time on big mailboxes and requires an internet connection.
Everyday habits that keep Mail from taking up too much space on Mac
- Save and remove big attachments from long email threads. If friends send frequent photos or PDFs, save them to Documents or Pictures, then use Message > Remove Attachments on those emails.
- Empty junk and deleted folders periodically with Mailbox > Erase Junk Mail and Mailbox > Erase Deleted Items for each account. (Menu names may vary slightly by account type and version.) (According to Apple documentation, details may vary by version.)
- Use Mail Drop for sending large files. Recipients download from iCloud and your Mac does not keep giant copies in Sent. Mail Drop supports very large attachments when your provider has limits.
A short story: Maria’s “mystery” 18 GB
Maria, a retired teacher, noticed her Mac’s fan came on more often and her storage bar was almost full. Storage showed Mail using 18 GB. We opened Mail, sorted by Size, and found monthly newsletters with photo-heavy PDFs. We saved the PDFs she needed to a “Travel and Family” folder, then used Message > Remove Attachments for those emails. In five minutes, Mail dropped to 7 GB. We then set Download Attachments to Recent so future downloads would be slimmer. Her Mac felt quiet and spacious again.
Key takeaways
- If Mail is taking up too much space on Mac, attachments are usually the reason.
- Remove Attachments keeps your emails and frees space.
- Set Download Attachments to Recent or None, and consider the Storage recommendation to keep only recent attachments.
If this helped, you will enjoy the gentle, step-by-step approach in “Learning Mac for Absolute Beginners – macOS 26, 2026 edition.” It covers storage, Mail, and the everyday basics, with calm explanations and clear steps you can follow at your pace.