Email headers in a message can provide you with valuable information about the message such as its sender, its return path, etc.

Here is how you can view all email headers in a message, depending on what mail client you are using (the instructions assume you have selected the message whose headers you want to see):

• Webmail
  • Horde - click Show All Headers located in the Headers section above the email's body;
  • SquirrelMail - click View Full Header located in the Options section above the email's body;
  • RoundCube - click the Show Source button (a folded page with an S in the middle) located above the message;
• Mozilla Thunderbird - go to View > Message Source; you can also use Ctrl + U
• Mac Mail - go to View > Message > Long Headers;
• Entourage - go to View > Options > Internet Headers;
• Microsoft Outlook Express - go to File > Properties > Details > Message Source;
• Microsoft Outlook 2003 - go to View > Options > Internet Headers;
• Microsoft Outlook 2007 - go to Options > Internet Headers;
• Opera - right-click on the message > View All Headers and Message;
• Google Email/Gmail - click the down arrow button next to Reply and choose Show original;