An email message consists of the following general components:
The message headers contain information concerning the sender and recipients. The exact content of mail headers can vary depending on the email system that generated the message. Generally, headers contain the following information:
Subject. Subject is a description of the topic of the message and displays in most email systems that list email messages individually. A subject line could be something like "2009 company mission statement" or, if your spam filtering application is too lenient, "Lose weight fast!!! Ask me how."
Sender (From). This is the senders Internet email address. It is usually presumed to be the same as the Reply-to address, unless a different one is provided.
Date and time received (On). The time the message was received.
Reply-to. This is the Internet email address that will become the recipient of your reply if you click the Reply button.
Recipient (To:). First/last name of email recipient, as configured by the sender.
Recipient email address. The Internet mail address of the recipient, or where the message was actually sent.
The body of a message contains text that is the actual content, such as "Employees who are eligible for the new health care program should contact their supervisors by next Friday if they want to switch." The message body also may include signatures or automatically generated text that is inserted by the sender's email system.
Attachments are optional and include any separate files that may be part of the message.