If you send a lot of emails on your iPhone or iPad that go to different people, you may want to blind copy some users, or all of them for that matter, so they don't see each other's email addresses. Regardless of the reason, if you forget there isn't a need to delete the email and re-enter it in the appropriate field. iOS actually gives you the ability to move them pretty seamlessly.
If you're writing an email on your iPhone, iPod touch, or iPad and you don't have time to finish, or you're simply not sure you're ready to send it yet, you can always save it as a draft and come back to it later. However, it can take a lot of hunting actually find that draft and get back to it! Luckily, iOS contains a gesture shortcut that can make tracking down all your draft emails a lot faster.
If you come back to your iPhone, iPod touch, or iPad only to find a ton of new emails you really don't want to go through, or if you opened an email by accident but don't want to forget about it later, you can easily mark one or more messages as read or unread right in the built-in Mail app.
The iPhone and iPad are great for quickly handling email. However, if something is important, or requires a lengthy reply, or you can only get to it later, or you simply want to keep your inbox close to zero, the iPhone and iPad are also great for quickly sorting and filing your mail into well organized mailboxes.
If you got a lot of email, you might want to start managing it better by filing it away into specific mailboxes. You can have separate mailboxes for certain people, for projects at school or at work, for sorting important messages you want to deal with immediate, from things you want to keep handy to reference later. Best of all, you can create new mailboxes right on your iPhone, iPod touch, and iPad.
Sometimes you get an email that you want to easily find again later, maybe to follow up, maybe just to keep handy. Luckily, your iPhone, iPod touch, and iPad Mail app comes with this functionality built right in. All you have to do to keep special track of a message is flag it. Then you can read, reply, or refer to again quickly and easily, whenever you need to.