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.
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About message headers
After you compose a message and send it, the message is processed by the email server at your Internet service provider (ISP). If the message is for someone who does not have a mailbox on your email server, the server forwards the message to another email server. The message is forwarded from server to server. It may go through several email servers until it reaches the email server on which the recipient of the message has a mailbox.
From the time when the message is first created, information about it is added to a hidden section of the message known as the Internet header. The information includes technical details, such as who created the message, the software used to compose it, and the email servers it passed through on its way to the recipient. You can use these details to identify problems with the email message or help discover the sources of unsolicited commercial email messages.
Note: The practice of providing false information in message headers is a growing problem. This is also known as spoofing. For example, a message might indicate that it is from Eric Lang at Alpine Ski House (firstname.lastname@example.org) when it is actually from a bulk email service that promotes schemes to get rich quickly. Therefore, before you send an angry reply to someone complaining about his or her message, remember that the header information might be forged.
View message headersIn Outlook 2016, 2013, or 2010
In an open email message, click the File tab.
On the Info tab, click Properties.
Header information appears in the Internet headers box.
Open an email message.
On the Message tab, in the Options group, click the Dialog Box Launcher .
In the Message Options dialog box, the headers appear in the Internet headers box.
Consider an email exchange between two people, Anton Kirilov and Kelly J. Weadock. Anton's email address is email@example.com and Kelly's address is firstname.lastname@example.org. Kelly uses Microsoft Office Outlook 2007. The Internet header associated with Kelly's message to Anton looks as follows:
Microsoft Mail Internet Headers Version 2.0Received: from mail.litwareinc.com ([10.54.108.101]) by mail.proseware.com with Microsoft SMTPSVC(6.0.3790.0);Wed, 12 Dec 2007 13:39:22 -0800Received: from mail ([10.54.108.23] RDNS failed) by mail.litware.com with Microsoft SMTPSVC(6.0.3790.0);Wed, 12 Dec 2007 13:38:49 -0800From: "Kelly J. Weadock" <email@example.com>To: <firstname.lastname@example.org>Cc: <email@example.com>Subject: Review of staff assignmentsDate: Wed, 12 Dec 2007 13:38:31 -0800MIME-Version: 1.0Content-Type: multipart/mixed;X-Mailer: Microsoft Office Outlook, Build 12.0.4210X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165Thread-Index: AcON3CInEwkfLOQsQGeK8VCv3M+ipA==Return-Path: firstname.lastname@example.orgMessage-ID: <MAILbbnewS5TqCRL00000013@mail.litware.com>X-OriginalArrivalTime: 12 Dec 2007 21:38:50.0145 (UTC)
Note: The sample header might not contain all items found in your email headers. These are the most common entries.
When Kelly sends an email message to email@example.com, she composes it from her computer, which is identified as (i101-177.nv.litwareinc.com). The composed text is passed from her computer to the email server, mail.litwareinc.com. This is the last that Kelly will see of her email message, because further processing is handled by email servers with no intervention from her. When Kelly's email server receives the message for firstname.lastname@example.org, it contacts Proseware's email server and delivers the message to it. The message is stored on the proseware.com server until Anton checks his Proseware email messages.
The following is an explanation of the common email header fields.
Microsoft Mail Internet Headers Version 2.0
This header is added by Outlook.
Received: from mail.litwareinc.com ([10.54.108.101]) by mail.proseware.com with Microsoft SMTPSVC(6.0.3790.0);
Wed, 12 Dec 2007 13:39:22 -0800
This information says that the message transfer occurred on Wednesday, December 12, 2007, at 13:39:22 (1:39:22 in the afternoon) Pacific Standard Time (which is 8 hours later than Coordinated Universal Time (Greenwich Mean Time); thus the "–0800").
Received: from mail ([10.54.108.23] RDNS failed) by mail.litware.com with Microsoft SMTPSVC(6.0.3790.0);
Wed, 12 Dec 2007 13:38:49 -0800
This message transfer occurred on Wednesday, December 12, 2007, at 13:38:49 (1:38:49 in the afternoon) Pacific Standard Time (which is 8 hours later than Coordinated Universal Time (UTC); thus the "–0800").
From: "Kelly J. Weadock" <email@example.com>
This message was sent by Kelly J. Weadock from the email address firstname.lastname@example.org.
This is the person to whom the email message is addressed.
These are the person or persons who receive carbon copies of the message.
Note: Recipients of blind carbon copies (Bcc) do not appear in the header.
Subject: Review of staff assignments
This is the subject of the email message.
Date: Wed, 12 Dec 2007 13:38:31 -0800
This indicates the date and time that the email message was sent, based upon the computer clock on the sender's computer.
This parameter specifies the version of the MIME protocol that was used by the sender.
This is an additional MIME header. It tells MIME-compliant email programs about the type of content to expect in the message.
X-Mailer: Microsoft Office Outlook, Build 12.0.4210
This information indicates that the message was sent by using Microsoft Office Outlook with a build version of 12.0.4210.
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165
This entry indicates the email software (MIME OLE software) used by the sender.
This header is used to associate multiple messages with a similar thread. For example, in Outlook, the conversation view uses this information to find messages from the same conversation thread.
This entry specifies how to reach the message sender.
The message has been assigned this number by mail.litware.com for identification purposes. This ID will always be associated with the message.
X-OriginalArrivalTime: 12 Dec 2007 21:38:50.0145 (UTC)
This is a time stamp placed on the message when it first passes through a server running Microsoft Exchange.