How do I view full mail headers in Outlook?

First, let's look at what we mean by mail headers. Here's an example:

Return-Path: <lnotenboom@hotmail.com>
Delivered-To: 1-leo-clean_nospam@pugetsoundsoftware.com
Received: (qmail 13384 invoked by uid 110); 13 May 2005 21:33:53 -0000
Delivered-To: 1-leo_nospam@pugetsoundsoftware.com
Received: (qmail 13380 invoked from network); 13 May 2005 21:33:53 -0000
Received: from bay107-f18.bay107.hotmail.com (HELO hotmail.com) (64.4.51.28)
  by pugetsoundsoftware.com with SMTP; 13 May 2005 21:33:53 -0000
Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC;
     Fri, 13 May 2005 14:33:53 -0700
Message-ID: <BAY107-F18247D6C6473F92CC602D8D2120@phx.gbl>
Received: from 64.4.51.220 by by107fd.bay107.hotmail.msn.com with HTTP;
    Fri, 13 May 2005 21:33:52 GMT
X-Originating-IP: [64.4.51.220]
X-Originating-Email: [lnotenboom@hotmail.com]
X-Sender: lnotenboom@hotmail.com
From: "Leo Notenboom" <lnotenboom@hotmail.com>

To: leo_nospam@pugetsoundsoftware.com
Bcc: 
Subject: Example Email
Date: Fri, 13 May 2005 14:33:52 -0700
Mime-Version: 1.0
Content-Type: text/plain; format=flowed
X-OriginalArrivalTime: 13 May 2005 21:33:53.0097 (UTC) FILETIME=[75980390:01C55803]

Now headers on any given message may look a lot different. It may be longer or shorter, or have additional information, or less. But the basic idea is that there's a lot of information in the headers that has to do with the administration of getting the email from the sender to the receiver.

Most email clients hide all that and show you only the stuff you care about: "To:", "From:", "Subject:", date and time, that kind of thing. It's rare that you actually need to see everything else.

To actually view the mail headers of a message, the steps are naturally different for each mail client.

Outlook

For Outlook 2010 (and possibly 2007) see: How do I view full headers in Outlook 2010?

In previous versions: right-click on the message in the message list:

Click on Options, and you should see a dialog box similar to this:

The section labeled "Internet headers:" contains the full internet headers for the message. Unfortunately it's almost always too small to show them completely. While you can scroll up and down within that box, I find it easier to copy them to notepad to view. Click in the headers, type Ctrl+A, followed by Ctrl+C to select all the headers and copy them to the clipboard, than then open notepad and click on the Edit menu, and then Paste.

Outlook Express

Outlook Express is naturally different. Right click on the message in the message list, and this time select Properties. Click on the Details tab in the resulting dialog, and you should see something like this:

This time, however, the box with the internet headers cannot be so easily copy / pasted into another application. Instead, you can press the Message Source button and get the entire message, including its headers, in a resizable, scrollable window (that you can copy / paste from, if you like).

Thunderbird

Thunderbird is perhaps easiest of all in this regard. Just click on the little boxed plus sign at the top of the message, and the header will expand to show all entries:

In Thunderbird 3, click on "other actions", and select the "view source" item to view the entire original source of the email message, including the message headers.

Mail clients, including free email services, are all different. Some may display full headers by default, others will hide them, but provide some way, perhaps obscure, to view them.

The good news is that it's rare you'd actually need to see them anyway.

(Updated April 17, 2011 for Outlook 2010 and Thunderbird 3.)