How to Recover Email Header in Webmail

To recover the email header in StarterMail webmail, follow the below steps:

Login to webmail
Open the required email message
Click on "Details"
Click on "All headers..."

A pop-up will open, containing all message headers in plain text.

The email header is something like this:

Return-Path: <john.doe@example.com>
Delivered-To: mario.rossi@domainregister.si
Received: from 156.unihost.it
by 156.unihost.it with LMTP
id 0AAOKzXP6mCaYwAAnadOvw
(envelope-from <john.doe@example.com>)
for <mario.rossi@domainregister.si>; Sun, 11 Jul 2021 13:00:05 +0200
Return-path: <john.doe@example.com>
Envelope-to: mario.rossi@domainregister.si
Delivery-date: Sun, 11 Jul 2021 13:00:05 +0200
Received: from www313.your-server.de ([88.198.176.136])
by 156.unihost.it with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
(Exim 4.94.2)
(envelope-from <john.doe@example.com>)
id 1m2XBt-0000K9-4J
for mario.rossi@domainregister.si; Sun, 11 Jul 2021 13:00:05 +0200
Received: from sslproxy01.your-server.de ([78.46.139.224])
by www313.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256)
(Exim 4.92.3)
(envelope-from <john.doe@example.com>)
id 1m2XBs-0008OG-Ux
for mario.rossi@domainregister.si; Sun, 11 Jul 2021 13:00:04 +0200
Received: from [92.60.66.69] (helo=example.com)
by sslproxy01.your-server.de with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256)
(Exim 4.92)
(envelope-from <john.doe@example.com>)
id 1m2XBs-0005M4-Qa
for mario.rossi@domainregister.si; Sun, 11 Jul 2021 13:00:04 +0200
Date: Sun, 11 Jul 2021 13:00:04 +0200
To: Mario Rossi <mario.rossi@domainregister.si>
From: John Doe <john.doe@example.com>
Reply-To: John Doe <john.doe@example.com>
Subject: happy birthday from John Doe!
Message-ID: <FpFJ7DXCfGLL3u88Yf7GB40utCAe8Ox6qdQvnyGy3w@example.com>
X-Mailer: Example Email Services
MIME-Version: 1.0
Content-Type: multipart/alternative;
boundary="b1_FpFJ7DXCfGLL3u88Yf7GB40utCAe8Ox6qdQvnyGy3w"
Content-Transfer-Encoding: 8bit
X-Authenticated-Sender: john.doe@example.com
X-Virus-Scanned: Clear (ClamAV 0.103.2/26227/Sat Jul 10 13:20:21 2021)
X-Antivirus-Scanner: Clean mail though you should still use an Antivirus

It contains a lot of technical information about the message, useful i.e. to understand:

why a message is marked as spam
why a spam message is not marked as spam by the system
why a message has not been delivered, as should happen, in a short time, but required hours or days to be delivered

... and many other kinds of possible technical issues.

Every time you require support for a received message, specify the header of the message too in plain text format (just copy / paste it), and not as a screenshot!

NOTE:

email headers may be recovered also by any email client: Thunderbird, Outlook, Microsoft Mail... to recover the email header using your email client, please refer to the documentation of the email client you're using.
this guide is valid not only for StarterMail service, but for any email service using RoundCube webmail