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...

This has been said before many times and in many ways, but its worth reminding yourself  every now and then...:

When you see a requested action in an email, don't do it immediately. It might be one of the least important things for you to do that day. Instead, immediately identify what the action is and put the email in a task folder. Change the title so that it states what you need to do, and put a due date on it and a priority level. You can do that in 15 or 20 seconds. Then you move right on to the next email. Now you'll get through your to-do email remarkably fast. Drag all of your other emails into a process folder, so you now have an empty inbox, which is a really nice feeling. The next thing you do is go to your task list and ask, What are the most important things I need to do today That's the stuff that would keep you from going home at the end of the day.

Michael Linenberger: Liberate tasks from your inbox | 43 Folders