1. Log in to Gmail
2. Open the message you'd like to view headers for.
3. Click the down arrow next to Reply, at the top of the message pane.
4. Select Show Original.

The full headers will appear in a new window.

1. Log in to your AOL account.
2. Open the message you'd like to view headers for.
3. In the 'Action' menu, select View Message Source.

The full headers will appear in a new window.

1. Log in to your Excite account.
2. Open the message you'd like to view headers for.
3. Click the View Full Headers icon located on the right of the 'From:" line.

The full headers for all of your messages will appear in a new window.

1. Log in to your Hotmail account.
2. Select Inbox from the left-side menu.
3. Right-click the message you'd like to view headers for and select View Message Source.

The full headers will appear in a new window.

1. Log in to your Yahoo! Mail account.
2. Select the message you'd like to view headers for.
3. Click the Actions dropdown and select View Full Header.

The full headers will appear in a new window.

1. Open Apple Mail.
2. Click on the message you'd like to view headers for.
3. Go to the View menu.
4. Select Message, then Long Headers.

The full headers will appear in the window below your inbox.

1. Open Mozilla.
2. Click on the message you'd like to view headers for.
3. Click the View menu, and select Message Source.

The full headers will appear in a new window.

1. Open Opera.
2. Click the message you'd like to view headers for so it displays in the window below your inbox.
3. Click Display all headers, across from the To field.

The full headers will appear in the window below.

1. Open Outlook.
2. Open a message.
3. On the Message tab, in the Options group, click the Dialog Box Launcher icon image.
4. In the Message Options dialog box, the headers appear in the Internet headers box.

For older versions of Outlook:

1. Open Outlook.
2. Open the message you'd like to view headers for.
3. Click the View menu, and select Options....

The full headers will appear in a new window.

1. Open Outlook Express.
2. From your inbox, locate the message you'd like to view headers for.
3. Right-click the message, and select Properties.
4. Open the Details tab in the dialogue box.

The full headers will appear in the dialogue box.