Outlook Express 4, 5 and 6
 
Start by opening the message in its own window (or when viewing the message in the preview pane). Then: 

With the keyboard: 

CTRL-F3 (Message Source Window) 
CTRL-A (select all) 
CTRL-C (copy) 
ALT-F4 (close) 
With the mouse: 

Click the "File" menu 
Click "Properties" 
Click the "Details" tab 
Click "Message Source" 
Highlight, copy and paste everything from this window (Ctrl-A, Ctrl-C) 
With viruses, worms and trojans being spread via email, many users now work with the preview screen in Outlook Express turned off. Viewing the contents of email in the preview screen is no different than opening the message. If the email has malicious content, it may execute in the preview screen. 

The following is instructions to obtain the full message source if you have the preview panel turned off: 

Using the keyboard: 

Highlight the message in the folder 
Press alt & enter - this will open a message information window 
Press Ctrl & Tab - this changes to the "Details" tab 
Press Alt & m - the opens the message source 
Press Ctrl & a - to select all the text 
Press Ctrl & c - to copy the selected text to the clipboard 
Press Alt & F4 - to close the message source window 
Press the Esc key - to close the information window  
 

 
Outlook 98 and 2000

Open the message in a separate window (double click) 
Under the View menu select Options 
Copy the text in the Internet Headers window (unfortunately it doesn't include the message itself). 
Paste 
Close the options window 


Microsoft Exchange
 
To get the complete headers and message source using Microsoft Exchange Click the "File" menu 
Click "Properties" 
Click the "Details" tab 
Click "Message Source" 
Highlight, copy and paste everything from the "Message Source" window (Ctrl-A, Ctrl-C)