Its been a while since the site has been updated and we are looking to add more email clients with steps to retrieve headers. If you have any email clients that are not in the list please let me know so I may add them

How to Display Full Headers in Apple Mail (Mac OS X)

The following steps are for displaying and forwarding the full headers of an email using the Mail application in Macintosh OS X:

With the Mail application open:

1. Open the “In” mailbox (Mailbox drop down menu -> Show -> In OR press cmd-1 on the keyboard ).
2. Click on the Email that you want to see the full header information for.
3. Click the View pull-down menu, and then choose Message and Long Headers, OR press Command-Shift-H on the keyboard.
4. Click the Forward button, OR click the Message pull-down menu and choose Forward Message, OR press command-shift-f on the keyboard.
5. Fill in the address in the “To:” field as well as the subject, then send the message.

How to Get Full Email Headers From SquirrelMail

• Sign in to your SquirrelMail Email account.a
• Click on the Email you wish to view headers for.
• Above the email you will see the following option; 
• Options: View Full Header | View Printable Version | Download this as a file
• Select View Full Header
• Copy the information that will appear on a new window and forward the ISP

How to Get Full Email Headers From PHPMailer

From the following site PHP Manual online.

In Apached:
function emu_getallheaders() {
foreach($_SERVER as $name => $value)
if(substr($name, 0, 5) == ‘HTTP_’)
$headers[str_replace(' ', '-', ucwords(strtolower(str_replace('_', ' ', substr($name, 5)))))] = $value;
return $headers;
}
?>

Non-Apache:
function emu_getallheaders() {
foreach($_SERVER as $h=>$v)
if(ereg(‘HTTP_(.+)’,$h,$hp))
$headers[$hp[1]]=$v;
return $headers;
}
?>

How to Get Full Headers From Pegasus

This will show you how to forward a message with headers still in place… with no formatting or wrapping of the headers, the best way is to forward the message as an attachment to a new email message.

This is done simply by:

(1) create new message and address as normal to whatever reporting agency/agencies such as spamhaus, SEC, SpamCop, etc.

(2) Use drag-and-drop the subject (SPAM) message into the new message.  When you do that, a dialog will appear giving options:

(3) In the “Drop message(s) into editor” dialog box, check the last check box at bottom of dialog box under heading “Attach or include message?” … here click “Add as attachment instead of including”

This way the entire message is attached, exactly as received, with no formatting or re-wrapping of headers or message body by Pegasus Mail.

The above is current as of Pegasus Mail version 4.41 and is believed to be accurate for many of the previous versions

Alternatively..

In Pegasus, just hit Ctrl-H (or the backspace key) while reading a message. You will see the full headers.
Do this *before* hitting “F” (for Forward), and the full headers will be forwarded, too.
(True for Pegasus 2.53, at least)

How to Get Full Email Headers From ZZN.com

Click on the “VIEW MESSAGE SOURCE” link in each mailbox you have.  This option will allow you to view full email headers

How to Get Full Email Headers From Yahoo! Mail

Yahoo! Mail has 2 interfaces, “Yahoo! Mail Classic” and “New Yahoo! Mail”.

Getting Full Headers from Yahoo! Mail Classic

Open the email message you want to view. Scroll to the bottom of the message and towards the bottom right corner you will see a blue toolbar that contains “Full Headers Link”. Click this link, and the full headers will be displayed at the top of the message.

When forwarding messages , you must copy and paste the full headers from the original message, as they will not normally be included.

Getting Full Headers from New Yahoo! Mail

Open the email message. Click the Actions button on the toolbar above the message and select “Full Header”. A prompt box will appear with the full headers.

When forwarding the message , you must copy and paste the full headers from this pop-up box along with the original message, as they will not normally be included.

How to Get Full Headers From Windows Live Mail 2009

Right Click on the email, Select properties, and Click on Details link to view the headers.

How to Get Full Email Headers From WebTV

When viewing the email message, click on “Forward” on the sidebar. Address the email to yourself and erase the subject line.

Put your cursor on the first line of the “body” (text area); Hit “Return” (enter) twice. Your cursor should now be on the 3rd line of the text area.

Type any “Alt” character on this line; DO NOT HIT “RETURN”

Cut and Paste the “Alt” character onto the subject line: (CMD+”A”), (CMD+”X”), (CMD +”V”)

The “Alt” character should “jump” down to the message text-area.

How to Get Full Headers From Verizon

Open the subject email in your browser, on the right side in red there is ‘message source’. Click it and a separate window will open with the header info.