How do I read the headers of my email?

The headers of email messages contain detailed information about the message. In the headers, you can find, for example, the sender of the message, the software used to create the email, and which mail servers the message passed through on its way to the recipient.

If you experience problems sending an email or receive unwanted mail, you can trace the source of the issue in the headers. In this article, we explain how to interpret the headers of email messages.

Read in this article how to view the headers of email messages when using Gmail, Outlook, the Mail app for iOS, Thunderbird, and the TransIP webmail.

In this article, we use the headers of an email message sent from Outlook 2016 via the TransIP mail servers. Below, you can see an email exchange between brothers Thijs (info@site-example.nl) and Emiel (info@email-example.nl).

Return-Path: <info@site-example.nl>
Delivered-To: info@email-example.nl
Received: from mdaproxy1.mail.transip.nl ([149.210.149.54])
    by webhosting127.transip.nl (Dovecot) with LMTP id kebVDbESZ1qiEwAA+IUPDg
    for <info@email-voorbeeld.nl>; Tue, 23 Jan 2018 11:47:13 +0100
Received: from mx3.mail.transip.nl ([149.210.149.87])
    by mdaproxy1.mail.transip.nl (Dovecot) with LMTP id kZLWLV7BZlpcPAAACHmHpw
    ; Tue, 23 Jan 2018 10:47:13 +0000
Received: from outbound1.mail.transip.nl (outbound1.mail.transip.nl [IPv6:2a01:7c8:7c8::72])
    (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))
    (No client certificate requested)
    by mx3.mail.transip.nl (Postfix) with ESMTPS id 3zQlNw0J6Wz5w9P
    for <info@email-example.nl>; Tue, 23 Jan 2018 11:47:12 +0100 (CET)
Received: from submission4.mail.transip.nl (submission4.mail.transip.nl [149.210.149.124])
    by outbound1.mail.transip.nl (Postfix) with ESMTP id 3zQlNv6ZDGzT52p
    for <info@email-example.nl>; Tue, 23 Jan 2018 11:47:11 +0100 (CET)
Received: from Thijs example (thijsie.site-example.nl [149.210.210.210])
    by submission4.mail.transip.nl (Postfix) with ESMTPA id 3zQlNv1HGJznWDV
    for <info@email-example.nl>; Tue, 23 Jan 2018 11:47:11 +0100 (CET)
From: <info@site-example.nl>
To: <info@email-example.nl>
Subject: Weekend getaway!!!!
Date: Tue, 23 Jan 2018 11:47:09 +0100
Message-ID: <003b01d39437$851ed9a0$8f5c8ce0$@site-example.nl>
MIME-Version: 1.0
Content-Type: multipart/alternative;
    boundary="----=_NextPart_000_003C_01D3943F.E6E38FC0"
X-Mailer: Microsoft Outlook 16.0
Thread-Index: AdOUN4IzpaYJD3JWQoOxeqk1jOyvtw==
Content-Language: en
X-Report-Abuse-To: abuse@transip.nl

Below is an explanation of the common fields you will find in headers.

Return-Path: <info@site-example.nl>

This field indicates how the sender of the message can be reached.

Delivered-To: info@email-example.nl

This field shows to whom the message was sent.

Received: from mdaproxy1.mail.transip.nl ([149.210.149.54])

    by webhosting127.transip.nl (Dovecot) with LMTP id kebVDbESZ1qiEwAA+IUPDg

    for <info@email-example.nl>; Tue, 23 Jan 2018 11:47:13 +0100

In addition to the fields above, you will see a series of 'Received:' fields. These fields indicate which mail servers the email passed through and which mail software was used. You can also see the date and time the email reached each mail server. In this case, the message was sent on January 23, 2018, at 11:47:13 (CET).

From: <info@site-example.nl>

This field shows from which email address the message was sent.

To: <info@email-example.nl>

This field shows to which email address the message was sent. 

Subject: Weekend getaway!!!!

This field contains the subject of the email message.

Date: Tue, 23 Jan 2018 11:47:09 +0100

Here you can see the date and time when the message was actually sent. The sender’s computer clock is used for this.

Message-ID: <003b01d39437$851ed9a0$8f5c8ce0$@site-example.nl>

This field contains the identification number of the message, created by site-voorbeeld.nl. This ID will always be associated with the email message.

MIME-Version: 1.0

This field shows the version of the MIME protocol used by the sender.

Content-Type: multipart/alternative; 
    boundary="----=_NextPart_000_003C_01D3943F.E6E38FC0"

This field provides information to email programs that use MIME about the type of content expected in the message.

X-Mailer: Microsoft Outlook 16.0

This field indicates which version of Outlook was used to send the email.

Thread-Index: AdOUN4IzpaYJD3JWQoOxeqk1jOyvtw==

The Thread-Index is used to link multiple messages in a conversation thread.

Content-Language: en

This shows the language of the message content.

X-Report-Abuse-To: abuse@transip.nl

Fields that start with 'X' are not standard but are added by the mail servers that send the email message. In this case, our system added the email address that can be used to report the message if it is suspected to be unwanted, such as spam or phishing.

As mentioned, any problems with sending or receiving emails can be found in the headers. Check whether, in addition to the general fields and X-headers, there are any error messages. Based on this information, you may be able to identify and resolve the issue.

If you can’t figure it out, please contact our support department via the 'Contact us' button below this article. Don’t forget to include the headers of your email.