Outlook: Sending Unsent Messages

I imported a comma-delimited file into my Outbox folder and tried to use the file to create and send messages. However, the messages never left the Outbox folder. How can I get Outlook to send these messages?

Open each message, then choose Actions, Resend This Message. If you receive the You do not appear to be the original sender of this message. Are you sure you want to resend it? warning, click Yes. The message will then appear with recipients' names in the To box; click Send.