There's a few potential causes for outgoing messages being queued. The most common reason is your email app client can't communicate with the mail server. Messages you are attempting to send are waiting to connect with the outgoing mail server to be handed off.
Can you give us some additional information about your email configuration? Is it Exchange, POP, IMAP, Gmail, Yahoo, AOL, etc?
Are you utilizing the native Email app that came installed on your phone or a third party app like BlueMail, Nine, or Touchdown?
Also it can come in handy to know the version of Android you're running and model of your device.