1. Press the Home button and choose Settings.
2. Scroll down and click Mail, Contacts, Calendars.
3. Tap your email account.
4. Scroll to the bottom and click Advanced.
5. Scroll to the bottom and tap the empty IMAP Path Prefix.
6. Enter INBOX in capitals
Note: You may need to click ‘Done’ at the bottom of the screen although this doesn’t appear for everyone. Clicking the “account” button at the top left of the screen followed by “Done” on the top right of the next screen maybe enough to save the setting.
7. Press the Home button and then re-open Mail.
8. You will now be able to delete or move your emails on your iPhone.