You can save a message that you are in the process of composing and complete it later by doing the following:
Click the Save Draft button at the bottom of the Compose mail screen.
To retrieve the message, select the Drafts folder and double click on the message header and complete the message.
Note
Once you have completed the message you click the Send Now button to send it immediately.
You can click the Send Later button if you want to compile other messages before sending them out.