Generally your email will be sent as soon you finish composing it. If you are in your email program, when you are finished you simply click on the send button.
There are a few other situations when your email will not be sent right away.
First check your email settings. On outlook:
Tools > Options > Mail Set Up Make sure the 'send immediately when connected' box is checked
On Outlook Express:
Tools > Options > Send Make sure the 'send messages immediately' box is checked Also Tools > Options > General Make sure the 'send and receive messages at startup' is checked
If these settings are correct, then mail should be sent as soon as you send it.
However there are circumstances where this will not work. If you are in a different program then Outlook will hold onto your message until you go into the program and send the file.
For example, in Word you can go to:
File > Send To > Mail Recipient
This will in fact create the email message with your document as an attachment. However the message will not be sent until the next time you go into your Outlook program. The message will sit in your Outbox until that time.
Another common situation is if you click on an email link on a web site. Once you click your email message will be created for you. However, the message will wait in your In Box until you open Outlook and click on Send / Receive.
The mechanics of this will vary depending on what programs you have. Test it out for your self to see what happens.