An email header is the block of technical information that travels with every email, above the message body. It records who sent the message, who it was sent to, when, through which servers, and whether it passed authentication checks such as SPF, DKIM and DMARC. Most email clients hide it, but you can always display the full header.
Not to be confused with the newsletter header, which is the visible banner (logo, menu) at the top of a newsletter design.
The main email header fields
| Field | What it shows |
|---|---|
| From | The sender's name and address, as displayed to the recipient |
| To / Cc | The recipients the sender addressed |
| Subject | The subject line |
| Date | When the message was sent |
| Reply-To | Where replies go, if different from the From address |
| Return-Path | Where bounces are sent |
| Received | One line per server the message passed through, newest first |
| Message-ID | A unique identifier for the message |
| Authentication-Results | Whether the message passed SPF, DKIM and DMARC |
| List-Unsubscribe | The one-click unsubscribe link used by inboxes (see List-Unsubscribe header) |
How do you view an email's full header?
- Gmail: open the email, click the three dots next to Reply, then "Show original".
- Outlook: open the email, choose File, then Properties, and look at "Internet headers".
- Apple Mail: open the email and choose View, then Message, then All Headers.
Why do email headers matter?
Mailbox providers read headers to decide whether a message is genuine and where to deliver it. Senders read them to troubleshoot deliverability: the Authentication-Results line shows at a glance whether SPF, DKIM and DMARC passed. Headers also help spot phishing, because a From address can be faked but the Received and Return-Path lines are much harder to disguise. Mailpro sets up email authentication for your domain so these checks pass.
Frequently asked questions
Can an email header be faked? Some fields, such as From and Reply-To, can be forged, which is how spoofing works. Authentication results and the Received chain are what reveal it.
Does an email header contain my IP address? Webmail services such as Gmail usually do not include the sender's personal IP address; some desktop clients and servers can. The sending server's IP always appears in the Received lines.
Mailpro and email headers
Headers that pass every authentication check
Mailpro configures SPF and DKIM for your sending domain and manages unsubscribe links in your newsletters, so inboxes trust your emails. Swiss-hosted and GDPR-native.