If you've ever sent a message that you wished you hadn't - you may consider configuring Outlook to delay your outbound messages.
In Outlook, choose Tools->Options.
Go to the Mail Setup tab. Uncheck 'Send immediately when connected' and then click the Send/Receive button to the right.
Change the 'Schedule an automatic send/receive every..." to your desired time, perhaps 5 minutes.
If you ever want to speed that process up, you can always manually send/receive by cliicking the send/receive button.