iOS: If IMAP Mail folders are not visible
If you sync IMAP mail account settings from your computer to iPhone, iPad, or iPod touch, and the IMAP folders on your computer are all shown under your Inbox folder, then it might not work as expected on the device.
If this is the case, you may need to specify what is called an IMAP path prefix. You can enter the IMAP path prefix by choosing Settings > Mail, Contacts, Calendars > [ Tap your account] > [Tap your account again] > Advanced > IMAP Path Prefix. Here's an example of an IMAP mail account that requires a path prefix:
ISPs that require IMAP path prefixes usually provide instructions for configuring them, so check with your ISP or network administrator for additional information.