I get asked this so many times, I though I would save myself a bit of time, and publish a simple guide to setting up an iPhone for a POP3 or IMAP email account. Although the title says for cPanel, this guide is fine for just about any POP3 or IMAP account where you know the server and account details.
The screenshots were taken from my iPhone 4 runnng iOS 4.3.x. So, lets start.
Tap the Settings icon on your iPhone’s home screen. This will bring you to this screen (below).