Free up Yahoo Mail storage

Yahoo Mail keeps messages in your Yahoo account. This phone stores a local copy of recent mail, inline images, and attachments you downloaded. Clearing cache does not delete mailbox mail. Emptying Trash does.

See how much space Yahoo Mail is using

iPhone

Open the iPhone Settings app.
Tap General > iPhone Storage.
Tap Yahoo Mail.

Android

Open your phone Settings > Apps.
Tap Yahoo Mail.
Tap Storage or Storage and cache.

Attachments

Open a message with a large file.
If you tapped Download or Save, delete that copy in Files or Downloads when you no longer need it on this phone.

Downloaded attachments are user files. Clearing Yahoo Mail cache does not remove them. Deleting the email does not always delete a copy already saved outside the app.

Offline mail

The app keeps recent messages for offline reading. That is a local cache of mail, not a second mailbox. Signing out or clearing data drops the local copy. Mail stays on Yahoo unless you also deleted it there.

Trash and Bulk

Deleted mail goes to Trash. Empty Trash (and Bulk / Spam if you use those folders) to permanently remove messages from the account after Yahoo's retention window. That frees Yahoo mailbox space, not just phone cache.

Clear Yahoo Mail cache on Android

Open your phone Settings > Apps > Yahoo Mail.
Tap Storage or Storage and cache.
Tap Clear cache.

Do not tap Clear storage / Clear data unless you mean to sign out. Drafts that never sent may be lost.

Reinstall the app if storage is still high

If you already cleaned media and Yahoo Mail still looks huge, a fresh install can clear leftover cache and temp files that are hard to reach by hand.

Mail in your Yahoo account stays. Save Drafts and any attachments you downloaded only to this phone.
Delete the app from your phone.
Restart your phone.
Install Yahoo Mail again from the App Store or Google Play.
Sign in and restore from backup if the app offers it.

This often frees a lot of space. You may need to download some media again after restore.

What to do next

After Yahoo Mail is lighter, check your photo library for duplicates and similar shots. That is what Dedupo is for.

More app guides: Free up app storage.