How to interpret the mail header
The mail header! It's a treasure trove of information about the email you're reading. Here's a breakdown of how to interpret the various parts of an email header:
Header Structure
An email header is composed of multiple lines, each starting with a key-value pair, separated by a colon and a space. The lines are usually separated by a blank line. The header is divided into several sections:
- From: The sender's email address.
- To: The recipient's email address.
- Subject: The subject line of the email.
- Date: The date and time the email was sent.
- Message-ID: A unique identifier for the email.
- References: A list of message IDs related to this email (e.g., replies or forwards).
- In-Reply-To: The message ID of the email this email is a reply to.
- X- headers: Custom headers added by the email client or server.
Interpreting Specific Header Fields
Here's a brief explanation of some common header fields:
- From: The sender's email address. This can be a single address or a list of addresses separated by commas.
- To: The recipient's email address. Like the From field, this can be a single address or a list of addresses separated by commas.
- Subject: The subject line of the email. This is usually a brief summary of the email's content.
- Date: The date and time the email was sent, in the format
Day, DD MMM YYYY HH:MM:SS +0000
(e.g.,Wed, 12 Jan 2022 14:30:00 +0000
). - Message-ID: A unique identifier for the email, usually in the format
<[email protected]>
. - References: A list of message IDs related to this email. These can be used to track the conversation history of an email thread.
- In-Reply-To: The message ID of the email this email is a reply to. This helps email clients to correctly thread replies and forwards.
- X- headers: Custom headers added by the email client or server. These can provide additional information about the email, such as the sender's IP address or the email's priority level.
Tools for Analyzing Email Headers
If you're not familiar with email headers or need to analyze them in more detail, you can use various tools:
- Email clients: Most email clients, such as Gmail, Outlook, or Thunderbird, allow you to view the email header by clicking on the "Show original" or "View source" button.
- Email header analyzers: Online tools like Email Header Analyzer or Header Analyzer allow you to paste the email header and analyze its contents.
- Command-line tools: You can use command-line tools like
mail
ormutt
to view and analyze email headers.
By understanding the structure and content of an email header, you can gain valuable insights into the email's origin, routing, and delivery.