How to set up an IPhone device

Basic Setup

Following this guide you shall be able to configure your mail account on IPhone:

    NOTE: Although the password entry for the outgoing mail settings usually says "Optional", it isn't. 
          You will need to enter your username and password.

http://www.emacconsulting.com/email/how-to-create-imap-mail-account-on-iphone

Advanced Setup

Source: http://5thirtyone.com/apple/how-to-proper-gmail-imap-for-iphone-apple-mail/

Steps to properly configure IPhone Mail client so that Sent Mail, Deleted Mail, Drafts are reflected properly after syncing (back to the server):

1. Open Settings > Mail > [Your account] > Advanced
2. Select Drafts Mailbox > On the Server > Drafts. Return to the Advanced view.
3. Select Sent Mailbox > On the Server > Sent. Return to the Advanced view.
4. Select Deleted Mailbox > On the Server > Trash. Return to the Advanced view.

    NOTE: Also see Auto Purge.