IMAP e-mail accounts (such as Gmail and Hotmail) keep all of your e-mail on online servers, which means that you can't delete messages or read them unless you are online. Fortunately, you can set up your iPhone/iPod touch to copy your IMAP messages onto the device so that you can work with them offline. Here's how you do it:
- Go to Settings >Mail >your account name under Accounts >Advanced >Drafts Mailbox.
- Then under On My Phone, tap Drafts.
- Now go back and repeat step 2 for your Sent Mailbox and Deleted Mailbox folders