Have you ever started to write an email on the iPhone or iPad only to realize half-way through that you are not quite ready to send it yet and you need to turn your attention to other emails first? You don't have to lose all of the typing that you have done so far because the Mail app lets you save drafts and then go back to them later. Here is how.
The first step is to save what you have done so far as a draft. To do so, tap the Cancel button in the top left corner. This will give you the option to either delete the incomplete email or to Save Draft. Tap the Save Draft button.
Then, whenever you are ready to resume working on your draft email, you need to use the same icon at the bottom right corner of the main Mail screen that you tap on to start a new message ... but don't tap on that button. Instead, hold down on that button for about a second. This will cause a window to pop up showing you a list of all of your saved draft messages.
Simply tap on the email that you want to continue to working on, and then you'll find yourself right where you left off. You can go through this whole process again to save a new draft, or when you finally finish your email you can send it.
If you later decide that you no longer want to continue to save a draft of a message, just hold down the compose button to see the list of draft messages and then swipe across the message. A delete button will appear on the right.
The above images are all from an iPhone, but this works on the iPad, too.