Email, Messaging, & Video Calls Email How to View Full Message Headers in Mozilla Thunderbird Checking out headers can help you troubleshoot email problems Share Pin Email Print Email Yahoo! Mail Gmail By Heinz Tschabitscher Writer A former freelance contributor who has reviewed hundreds of email programs and services since 1997. our editorial process Heinz Tschabitscher Updated February 14, 2020 29 29 people found this article helpful Revealing the headers that are normally hidden in emails takes just a single step in Mozilla Thunderbird. The header can help you troubleshoot email problems. Headers in Email All emails consist of two parts: the header and the body. The standard header—which is the part you normally see—typically lists the sender and recipient of the message, date, and subject. Behind the scenes, though, the header contains much more information, such as the path it took from sender to recipient, the sender's IP address, and the message's priority. This information isn't particularly easy to interpret and isn't usually of interest to the recipient, so it's hidden. When you're asked to pass along all message headers to thwart a spammer or troubleshoot an email problem, or if you're simply curious, you can reveal all the hidden info. Open Thunderbird. Click a message in the reading pane to open it in a new tab or window. Select View > Headers > All from the menu bar to display the full message headers. To return to the standard set of headers, select View > Headers > Normal from the menu. Viewing a Message's Source If you want to see or need to copy the header lines in their original unformatted state, open the message's source in Mozilla Thunderbird by selecting View > Message Source. The source code is more extensive than just headers and includes the coding for the entire email.