You can save a draft to finish later, or look at existing email messages while you’re writing a new one.
Go to the Mail app on your iPad.
Tap in the upper-left corner.
Tap Edit at the top of the list.
Tap Add Mailbox, then turn on the All Drafts mailbox.
While you’re working on a draft, swipe down. Tap any thumbnail to open the draft, then continue editing.