How to Create E-Mail Messages in Outlook 2013
Click the Send button (or press Ctrl+Enter or Alt+S).
Your mail is moved to the Outbox. If your computer is online, Outlook immediately sends any messages from the Outbox. If Outlook is configured to not immediately send messages (as might be the case in some offices), you can press F9 (or select Send/Receive and click the Send/Receive All Folders button in the Ribbon) to send any e-mail messages that are queued up in the Outbox.
If you composed messages while your computer was offline, you can press F9 to send your messages when it’s again connected to the Internet. When a message is sent, it automatically goes to the Sent Items folder.