The headers of a message, also called the envelope or header, contain technical information about the email, such as the sender, the recipient, the software used to compose and send it, as well as the mail servers through which it passed to reach the recipient.
They are therefore particularly useful for:
- Identifying the true sender of the emails you receive, especially unwanted ones
- Tracking and analysing the transit path of the message: its journey and the servers through which it was routed
- Resolving certain sending/receiving issues, especially in case of significant reception delays or non-receipt/delivery failure
Message headers may in particular be requested from you to diagnose an email problem. In this case, retrieve the complete header (or text) by following the procedure indicated below according to the email application you use, then copy and paste the full header in text format into the body of your email or as an attachment.
Refer to the header retrieval procedure indicated for your email application/client. If you cannot find the email application/client you use, consult the official support and assistance site of your email application/client.
You can find a list with explanations here: How to Get Email Headers.