Postfix: suppress authenticated sender name in header

For different reasons I use a lot of alias email addresses. But do they really work like I think they should?

Let’s say I have my main email account called “info@my-domain.com”. For this address I have multiple email aliases like “admin@my-domain.com”,  “hello@my-domain.com” or even “info@another-domain.com”.

To handle those on the client side I use Mozilla Thunderbird. All the email aliases (except the main address “info@my-domain.com” of course) are setup as identities via Edit/Account Settings/info@my-domain.com/Manage Identities. This way I can send and receive emails for “info@my-domain.com”, “admin@my-domain.com”, “hello@my-domain.com” or “info@another-domain.com” (when writing an email just choose the right identity in the from field) with only one real email account. All these alias email addresses appear discrete for recipients.

So far so good, works like a charm.

BUT having a closer look at the header generated when we send an email from e.g. “info@another-domain.com” to “recipient@receiving-domain.com” we see something like this:

Return-Path: <info@another-domain.com>
Received: from mailin60.aul.receiving-domain.com ([xxx.xxx.xxx.xxx])
        by ehead902.aul.receiving-domain.com (Dovecot) with LMTP id M+LMKqUu8FU15gAAUDv/bw;
        Wed, 09 Sep 2015 15:05:56 +0200
Received: from mail.my-domain.com ([xxx.xxx.xxx.xxx]) by mailin60.aul.receiving-domain.com
        with (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384 encrypted)
        esmtp id 1ZZf4W-0ky3vc0; Wed, 9 Sep 2015 15:05:56 +0200
Received: from localhost (localhost.localdomain [127.0.0.1])
        by mail.my-domain.com (Postfix) with ESMTP id A07D232326E
        for <recipient@receiving-domain.com>; Wed,  9 Sep 2015 15:05:55 +0200 (CEST)
Received: from mail.my-domain.com ([127.0.0.1])
        by localhost (mail.my-domain.com [127.0.0.1]) (amavisd-new, port 10024)
        with ESMTP id 8McLKEgykSSF for <recipient@receiving-domain.com>;
        Wed,  9 Sep 2015 15:05:54 +0200 (CEST)
Received: from [xxx.xxx.xxx.xxx] (f055219075.isp.com [xxx.xxx.xxx.xxx])
        (Authenticated sender: info@my-domain.com)
        by mail.my-domain.com (Postfix) with ESMTPSA id 4BDCA32326B
        for <recipient@receiving-domain.com>; Wed,  9 Sep 2015 15:05:54 +0200 (CEST)
To: recipient@receiving-domain.com
From: "Postmaster nerd-quickies.net" <info@another-domain.com>
Subject: TestB
Message-ID: <55F02EB1.90701@another-domain.com>
Date: Wed, 9 Sep 2015 15:05:53 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101
  Thunderbird/38.2.0
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit

Normally I use alias email addresses to protect my main address from spam or to create the illusion that I send an email from a separate, discrete email account. So what I don’t want is, that my main email address is exposed to the public like it is in line 16 of the above header listing.

How do we get rid of this header line?

If you have your own postfix server it’s a very easy task.

Just open your /etc/postfix/main.cf and find this line:

smtpd_sasl_authenticated_header = yes

Change this to

smtpd_sasl_authenticated_header = no

, do a reload

postfix reload

and you are done. The “Authenticated sender line” will be suppressed completely from now on.