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 origina
