Email message headers provide a list of technical details about the message, such as who sent it, the software used to compose it, and the email servers that it passed through on its way to the recipient. For information on getting your full message headers, please refer to How do I view my email message headers?
Partial headers are what you normally look at in your emails. The partial headers are the most important to your daily tasks. Such headers are the From Address, To Address, Subject, Date and Time, Reply To Address, CC, and BCC. The full headers are simply more technical information than you normally see when you check your email. This information can be helpful for troubleshooting and investigating mail flow.
It is important to know that when reading an email header every line can be forged, so only the Received headers that are created by your service or computer should be completely trusted. The easiest way for finding the original sender is by looking for the X-Originating-IP header. This header is important since it tells you the IP address of the computer that had sent the email. If you cannot find the X-Originating-IP header, then you will have to sift through the Received headers to find the sender's IP address.
From
- This displays who the message is from, however, this can be easily forged and can be the least reliable.
Subject
- This is what the sender placed as a topic of the email content.
Date
- This shows the date and time the email message was composed.
To
- This shows to whom the message was addressed, but may not contain the recipient's address.
Return-Path
- The email address for return mail. This is the same as "Reply-To:".
Envelope-To
- This header shows that this email was delivered to the mailbox of a subscriber whose email address is user@example.com.
Delivery Date
- This shows the date and time at which the email was received by your (mt) service or email client.
Received
- The received is the most important part of the email header and is usually the most reliable. They form a list of all the servers/computers through which the message traveled in order to reach you.
The received lines are best read from bottom to top. That is, the first "Received:" line is your own system or mail server. The last "Received:" line is where the mail originated. Each mail system has their own style of "Received:" line. A "Received:" line typically identifies the machine that received the mail and the machine from which the mail was received.
Message-id
- A unique string assigned by the mail system when the message is first created. These can easily be forged.
Mime-Version
- Multipurpose Internet Mail Extensions (MIME) is an Internet standard that extends the format of email. Please see http://en.wikipedia.org/wiki/MIME for more details.
Content-Type
- Generally, this will tell you the format of the message, such as html or plaintext.
X-Spam-Status
- Displays a spam score created by your service or mail client.
X-Spam-Level
- Displays a spam score usually created by your service or mail client.
Message Body
- This is the actual content of the email itself, written by the sender.