Delete or Move IMAP Emails on iPhone
Posted by Vipin Nehra on 11 April 2016 09:19 PM
  1. Press the Home button on your iPhone and choose Settings.
  2. On the Settings screen, tap Mail, Contacts, Calendars.
  3. Click on your email account (it should display an arrow to the right of the email address.)
  4. Scroll down and click Advanced.
  5. Tap the empty IMAP Path Prefix.
  6. Enter INBOX (in capital letters), then click Accounts (top left) and click Done (top right) TWICE to close settings.
  7. Tap the Home button and then reopen email.

You will now be able to delete or move emails without an error message appearing!