This option is also noted as Send Immediately. If you enable this option, you can compose a message, push send, and the message will be placed in your Outbox waiting to be delivered. Then, at a later time, the mail program will send the messages for you. Or you could compose several messages, and leave them in the Outbox, and when you are ready to send the mail, you can select Send Queued Messages (found under the File menu). This will send all your messages at once.