How to Clear the Mail App Cache and Attachments on iPhone
The iOS Mail app caches downloaded messages and attachments locally, which is why Mail can show a large "Documents & Data" figure under Settings › General › iPhone Storage › Mail. The most reliable way to reclaim that space is to remove and re-add the email account at Settings › Apps › Mail › Mail Accounts › [account] › Delete Account, then add it back — for IMAP and Exchange accounts this clears the local cache without losing any server-side mail, which simply re-syncs. This guide is for anyone whose iPhone storage screen shows Mail eating gigabytes and who wants to clear it safely.
TL;DR
- Mail's storage is mostly cached messages and downloaded attachments, shown as Documents & Data.
- Check the size at Settings › General › iPhone Storage › Mail.
- The reliable reset is to Delete Account under Settings › Apps › Mail › Mail Accounts, then re-add it.
- For IMAP and Exchange accounts this is safe — your mail lives on the server and re-downloads.
- POP accounts are the exception: their mail can live only on the device, so back up first.
Why is the Mail app taking up so much space?
Mail keeps a local copy of the messages and attachments it shows you so the app opens instantly and works offline. Every photo someone emails you, every PDF you tap to preview, and the bodies of messages going back weeks or months are cached on the device. Over time that cache grows quietly — a few large attachment-heavy threads can add up to gigabytes — and it shows up as Documents & Data in the storage breakdown rather than as the app's own size.
The app size itself is tiny and fixed because Mail is built into iOS. So when the storage screen says "Mail" is large, it's almost always the cached message and attachment data, not the program. That's good news: cached mail is reclaimable, because the authoritative copy lives on your mail server.
How do I check how much space Mail is using?
Start by confirming Mail is actually the culprit before changing anything:
- Open Settings › General › iPhone Storage.
- Wait for the per-app list to render, then scroll to Mail.
- Tap Mail to see its breakdown — the large number will be Documents & Data, not the app size.
- Note the figure so you can compare after clearing.
If Mail isn't near the top of that list, your space is going somewhere else — usually photos, video, or message attachments — and clearing Mail won't help much. In that case, storage full: what should I delete first is the better starting point.
How do I clear the Mail cache by re-adding the account?
iOS doesn't expose a "clear Mail cache" button, so the dependable method is to remove the account and add it back. Deleting the account from your iPhone only removes the local copy — it does not touch anything stored on your mail provider's servers (for IMAP and Exchange).
- Open Settings › Apps › Mail › Mail Accounts.
- Tap the account you want to clear (Gmail, iCloud, Outlook, your work Exchange, and so on).
- Tap Delete Account and confirm. This removes the locally cached messages and attachments for that account.
- Add the account back: in the same Mail Accounts screen tap Add Account, choose your provider, and sign in.
- Let it re-sync. Mail re-downloads only what it needs, so the cache starts small again.
After re-adding, recheck Settings › General › iPhone Storage › Mail and you should see Documents & Data drop substantially.
Can I shrink Mail storage without deleting the account?
Yes — these settings reduce how much Mail caches in the first place, so the bloat doesn't return as quickly. They live under each account's settings.
- Lower how far back Mail syncs: open Settings › Apps › Mail › [account] › Mail Days to Sync and choose a shorter window (for example, 1 Month instead of No Limit). Older messages stay on the server and still load when you open them.
- Avoid bulk-downloading attachments: don't tap to download every attachment you don't need, since each one is cached locally.
- Delete heavy attachment threads inside Mail itself, then empty the Trash mailbox so they're removed from the device.
| Action | What it does | Server mail affected? |
|---|---|---|
| Delete & re-add account (IMAP/Exchange) | Clears the entire local cache at once | No — re-syncs from server |
| Lower Mail Days to Sync | Caches fewer past messages going forward | No |
| Empty the Trash mailbox | Removes deleted messages from the device | Removes them server-side too |
| Skip downloading attachments | Prevents new attachment cache buildup | No |
Is it safe to delete and re-add my email account?
For most people, yes — but the safety depends entirely on your account type, so it's worth being precise.
Native behavior: IMAP, iCloud Mail, Gmail, and Exchange accounts keep the master copy of your mail on the server. Deleting the account from your iPhone removes only the cached local copy; re-adding it pulls everything back down. Nothing is lost, and even your folders and read/unread state re-sync.
The POP exception: older POP accounts can be configured to download mail to a single device and remove it from the server. If yours is POP, deleting the account could delete the only copy of those messages. Before touching a POP account, back up or move important mail elsewhere first — this is the one case where the re-add trick is genuinely risky.
What Cleanor adds — and can't do: Cleanor handles the other big driver of a full iPhone — duplicate photos, large videos, and stray files — locally, with nothing uploaded. It does not manage mailbox sync or touch your email accounts, so the Mail steps above are the right tool for mailbox cache, and a cleaner is the right tool for media clutter. They solve different halves of a full phone.
FAQ
Will deleting my email account from iPhone delete my emails?
For IMAP, iCloud, Gmail, and Exchange accounts, no — your mail lives on the server and re-downloads when you add the account back. The exception is POP accounts, which can store mail only on the device, so back those up before removing the account.
Why does Mail show large Documents & Data?
Documents & Data for Mail is the cache of downloaded messages and attachments the app keeps so it opens fast and works offline. It grows over time, especially with attachment-heavy threads, and re-adding the account or lowering Mail Days to Sync brings it back down.
Does lowering Mail Days to Sync delete old emails?
No. It only limits how many recent messages are cached on the device; older emails stay on the server and download on demand when you scroll back or search. It reduces local storage without losing access to anything.
How do I stop the Mail app from filling up again?
Set a shorter Mail Days to Sync window, avoid downloading attachments you don't need, and empty the Trash mailbox periodically. Those habits keep the local cache small so you rarely need to re-add the account.
Where to go from here
Clearing Mail's cache is the right fix for a bloated mailbox, but on most iPhones the bigger space drains are photos, videos, and message attachments. To tackle the message side, see how to clear iMessage attachments and free up iPhone storage. For everything else — duplicate and similar photos, large videos, and stray files — the phone storage cleanup solution and Cleanor for iOS scan your library locally and show exactly what will be removed before anything is deleted, with nothing uploaded.