I've been using Outlook for over 15 years, and until today I've never used the "Delay Sending Email" feature.  In fact the only uses I've seen suggested for it involve trying to pretend you were in front of your PC, when really you're off having fun elsewhere.

Then today I found this idea at Suite101.com

Have you ever hit 'Send' and at the same moment realised you forgot to include some information or an attachment?

Outlook (not Outlook Express) will allow you to set up a Mail rule to delay messages for whatever time period you choose.  This gives your brain a chance to catch up with your sending reflex and stop the message before it leaves your outbox.

* Click TOOLS, ==> Rules & Alerts.
* Click on New Rule ==> Start from a blank rule 
* Select 'Check message after sending ==> Next.
* Select 'On this machine only (for Exchange users)==> Next,
* Check 'Defer delivery by a number of minutes'.
* In the lower panel Click 'A number of'
* Set the counter to 1
* Click on OK ==>  Finish.

Now messages will hang around in your outbox for a minute before being sent. If you're going to remember the missing info, or attachment it will usually happen in that minute...