I'm running Mail 3 on Leopard, and all my accounts are IMAP, I just found something that surprised me (it could well have been there all the while).

When I had the following in my clipboard:

,

random.

...and paste whilst looking at an inbox in Mail, it created a new unread email with the contents as:

random.

So, if you copy this:

From: steve@apple.com
Subject: You're hired

Dear thingy, 

We liked your mad skillz so much, we're going to 
throw money at you.

And paste it in to Mail, you'll find a new email.

Might be fun for a practical joke at some point...