With most device models, copies of sent messages are automatically stored to your device’s Sent folder. When composing a message, you can also save a draft message without sending it. Only messages with content (text, media files, or recipients) can be saved.
To save a message, click Save message in the message editor dialog box. The message is saved to the Drafts folder in the Messages view.
When you save an existing draft, it is stored to the same location from where you opened it. Saving overwrites the old message.