- Press the Home button on your iPhone and choose Settings.
- On the Settings screen, tap Mail, Contacts, Calendars.
- Click on your email account (it should display an arrow to the right of the email address.)
- Scroll down and click Advanced.
- Tap the empty IMAP Path Prefix.
- Enter INBOX (in capital letters), then click Accounts (top left) and click Done (top right) TWICE to close settings.
- Tap the Home button and then reopen email.
You will now be able to delete or move emails without an error message appearing!