Full email headers: What are they and how to access them (Updated for 2024)

Internet email messages have hidden headers (that email technology people commonly call "full headers" or "email headers") that can help you trace the source of a message and these can come in very handy for troubleshooting email delivery issues or reporting spam.

You know about some email headers already. To, From, Subject, Date are all examples of email headers you see today in your email client. There's a whole bunch of other ones, too, though. Two of those other ones are particularly useful. First, the "Received" headers are tracing headers that show the IP addresses, domains and time stamp information of servers that handled this particular email message on its journey toward your inbox or spam folder. Second, the "Authentication Results" header can give you ideas on which IP address or domain to look up to try to find where to send a spam report. 

Google even helps to extract and summarize bits of this info. When viewing the "Original Message" in Gmail, they break out Message ID, Created at, From, To, Subject, SPF, DKIM and DMARC results above the full headers and email source. Pay attention to the email authentication results (SPF, DKIM and DMARC), any of those showing "pass" should generally give you confidence that a domain referenced there is truly a responsible party for that message (and a potential entity to complain to, if the message is unwanted).

Here's how to get access to the full header info in the most common web email clients.

• Gmail and Google Apps: Trace an email with its full headers
• AOL/Yahoo/Verizon: Use full headers to find delivery delays or a forged email’s true address in Yahoo Mail
• Outlook.com: View internet message headers in Outlook (click on "Web" tab)
• Apple's iCloud Mail: View long email headers in Mail on iCloud.com
• Comcast: Xfinity Connect Email Toolbar Options - Xfinity Connect Help (scroll down to "More Actions" and see where it says "View source")

When you've got that full header information you can use various online tools to see how many servers handled this email message in transit, and even break down how long it took to hand off mail from one server to the next. This can be handy to help identify whether or not a delivery delay happened inside of the ISP, or did it take a long time for the sending platform to make the initial connection and hand off to the ISP? Google, Microsoft and MXToolbox all offer versions of these header analyzer tools. 

Want to learn more about reading email headers? Here's some suggested reading.

• ARCLAB: How to Read and Analyze the Email Header Fields and Information about SPF, DKIM, SpamAssassin
• MediaTemple: Understanding an Email Header
• Lifewire: What Email Headers Can Tell You About the Origin of Spam

Here's how to use email headers to track ISP (internet service provider), MBP (mailbox provider) or ESP (email service provider) delivery delays.

Pro tip: When somebody asks you to send them email headers, don't send them a screen shot of the from address or email body. That's not what they're asking for. (And screen shot images aren't searchable; if somebody is trying to help you troubleshoot something, it is painful to have to manually read each line of a header in an image to try to find the right header.) Instead, send them a text file attachment containing all of the copied-and-pasted email header info, or full message source.