Hidden e-mail header information
Return-Path: When available, this line is almost always at the beginning and gives the mail server a return option in case delivery is not possible. The delivered e-mail address is identical to the one that the server receives via the “envelope-from” information.
Example: Return-Path: <return-address@example.com>
Received: Received lines are generated by the mail servers that are involved in the transfer. There are at least two of these lines per e-mail header since one server is used to send and one is used to receive. The lines reveal the e-mail’s transmission route including the date and address of the mail server involved (usually inside square parentheses)
- Example: Received: from hostname.example.com (hostname.example.com [xxxxxxxx])
- by mailserver.recipient.com with SMTP
- for <recipient@example.com>; Thu, 24 Dec 2015 17:36:20
Message-ID: Every e-mail contains this clear identification, mostly from the mail servers or from the sender’s mail program. The first part of the ID is made up of a character code, and the second part is a domain name, separated by an “@” sign.
Example: Message-ID: <434571BC.8070702@example.com>
Content-Type: In this line of the e-mail header you will find information about the type and character set of the text body. The individual parameters are separated by semicolons.
Example: Content-Type: text/plain; charset=UTF-8</recipient@example.com></return-address@example.com>