Custom return-path not working with Postfix

Hello, I have configured Postfix server to be used by our local Mautic instance. In Mautic, I have configured:

Code:
'mailer_from_name' => 'perlur group marketing', 'mailer_from_email' => 'dl-gl-marketing@perlur.cz', 'mailer_transport' => 'smtp', 'mailer_host' => 'glczwe-sp230001.ext.perlur.cz', 'mailer_port' => '465', 'mailer_user' => 'sys.app.mautic@perlur.cz', 'mailer_password' => 'intentionally removed', 'mailer_encryption' => 'ssl', 'mailer_auth_mode' => 'plain', 'mailer_spool_type' => 'memory', 'mailer_spool_path' => '%kernel.root_dir%/spool',

In additional, I have also configured "Custom return path (bounce) address " to "sys.app.mautic@perlur.cz", however I am unable to find this part of configuration in "app/config/local.php" - although the setting is persistent, so it must be saved somewhere! Does anybody know where?

However, when I use "Send test email" function, e-mail gets properly delivered to my Google for Work mailbox on a same domain (we use mail routing between GfW servers and out local Postfix solution for system users such as Mautic). E-mails are delivered directly from our Postfix server, we DO NOT use GfW SMTP relay. We have properly configured SPF to include both Google IP addresses and our own server addresses. So far, so good, however, if I look into the e-mail, I see following test e-mail gets delivered (as you can see below, "Return-Path: dl-gl-marketing@perlur.cz" is configured instead of sys.app.mautic@perlur.cz, which is the mailbox where Mautic is expecting to get bounce and unsubscribe e-mails. Does anybody have experience with mentioned behavior?
Code:
Received: from C105S135VM025.eu.tieto.com (10.34.8.67) by C105S135VM016.eu.tieto.com (10.34.8.54) with Microsoft SMTP Server (TLS) id 15.0.1156.6 via Mailbox Transport; Mon, 29 Feb 2016 12:50:56 +0200 Received: from C105S135VM025.eu.tieto.com (10.34.8.67) by C105S135VM025.eu.tieto.com (10.34.8.67) with Microsoft SMTP Server (TLS) id 15.0.1156.6; Mon, 29 Feb 2016 12:50:56 +0200 Received: from ebb08.tieto.com (10.42.239.172) by mailrelay.tieto.com (10.34.8.67) with Microsoft SMTP Server (TLS) id 15.0.1156.6 via Frontend Transport; Mon, 29 Feb 2016 12:50:56 +0200 X-AuditID: 0a2aefac-f795c6d000004f61-e8-56d4228f1afa Authentication-Results: tieto-auth Received: from glczwe-sp230001.ext.perlur.cz (glczwe-sp230001.ext.perlur.cz [37.157.195.48]) (using TLS with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ebb08.tieto.com (SMTP Mailer) with SMTP id 29.EB.20321.09224D65; Mon, 29 Feb 2016 12:50:56 +0200 (EET) Received: from www.perlur.cz (glczwe-sp230001.ext.perlur.cz [IPv6:2a02:2b88:2:1::1113:1]) (Authenticated sender: sys.app.mautic@perlur.cz) by glczwe-sp230001.ext.perlur.cz (Postfix) with ESMTPSA id 1867F283F44 for ; Mon, 29 Feb 2016 11:50:55 +0100 (CET) Message-ID: Date: Mon, 29 Feb 2016 11:50:55 +0100 Subject: Mautic test email From: perlur group marketing To: Marek Stopka MIME-Version: 1.0 X-Brightmail-Tracker: H4sIAAAAAAAAA12TW0gUURjHPTvjetz25Dib63FyK6cbGZldHgxMgiR6MbtKRWWjntzJdVd2 Zk2NQCuDIsqKkqRM6UIXN6ELFETFVpi95GWxpAyp6E5hDyFU1jnrrs32Mpz5/b9zvv/5/jOQ EwegBEmVTrxuxSWbLfz00w8y5zTIwYLMK39sWfsf9/NLwPLA+9UrwUZLdglxqZXEOzdnq8V5 sa2Zq1hWtffRLXMtyD4A4iEWFuLufbU8WwNBxsHgnrhRbsddr9rNB4AFioLfhG82H+RHX86Y 8LvgdapAiIRsfL8xg23ghen4/ceBWLa2CRKuOzwSOtQsZOHepiGOlU8QFuCO4XyGkZCIO0++ DZVwwkz8q7mHG13PxhdaP3MNADUZypoMZU2GshbAXQYJpKgoMytDV4nuySj2lF8DdCaW9G9t t8DTe2kBIEAgW9GaicECMVap1KrLA6AMmuQk5GBofJGnpNqpaM5Cr89FNHkCUqwUozFc5HOV yRLaMIVS2xh1kx2ai+g0BHkSmrWuu0BMHtM0n1ahFqsen1bo87oCAEOOHnvbwY4tUapriNcz 2iwAJkJeTkbpApWEUkUnZYRUEG9ENcG4ANgBoYzROdY+0UtKSdU21aVHauhmNZVtNiohxw6U 29hbINqNgsF0GtrETEtG+X/fJhjPHpYAKIVWeoOXzAPSKpRyTS0N97ehrsmUWiM01DsFjbBS MQINfR3o91ra1x6Rons+AUcA/HCiz2+CfY3s2TL8wm8SebfHTaRklJDGrsq2On3usRlIduRK okKCQWA2pFSU/Z2OIMnA/zmRpqAcpqYY1GgzkV+rBzgkGwIxMTGilYZTrurhu4f1T6CYfmE2 5GF3tqpu/d90RPSVTWdcGIaGg9EbxhLDzDCbVORgmSSFlWg3n2gIJhoCbu9hIeiKbgzh2FAv CyFMwyEcZlCMwKgQGphkj0jRnaRakLa0bO6zLJ1fN793RXxnW97XvON310yC4E9DymClr6W4 c9HNS4e659RJw9M+vqxPzovbe2qq9XmO5q/L3b91y8/08zUdg75C7suI+vrGw/4tV45s0OYv 3XV0/eangaGW7R1nM8yr3iwu/NHaenBGYsedmt1Xd9ZLsbnL87Xf/vr+9mk/ZV5zKvPSOa+m /AXeu1ro8AQAAA== Return-Path: dl-gl-marketing@perlur.cz X-MS-Exchange-Organization-Network-Message-Id: ce164047-dd4d-4df1-cd89-08d340f633c8 X-MS-Exchange-Organization-AVStamp-Enterprise: 1.0 X-MS-Exchange-Organization-AuthSource: C105S135VM025.eu.tieto.com X-MS-Exchange-Organization-AuthAs: Anonymous Content-type: text/plain; charset="UTF-8" Content-transfer-encoding: 7bit

Hi! This is a test email from Mautic. Testing…testing…1…2…3!

Hello, I have configured Postfix server to be used by our local Mautic instance. In Mautic, I have configured:

        'mailer_from_name' => 'perlur group marketing',
        'mailer_from_email' => 'dl-gl-marketing@perlur.cz',
        'mailer_transport' => 'smtp',
        'mailer_host' => 'glczwe-sp230001.ext.perlur.cz',
        'mailer_port' => '465',
        'mailer_user' => 'sys.app.mautic@perlur.cz',
        'mailer_password' => 'intentionally removed',
        'mailer_encryption' => 'ssl',
        'mailer_auth_mode' => 'plain',
        'mailer_spool_type' => 'memory',
        'mailer_spool_path' => '%kernel.root_dir%/spool',

In additional, I have also configured "Custom return path (bounce) address " to “sys.app.mautic@perlur.cz”, however I am unable to find this part of configuration in “app/config/local.php” - although the setting is persistent, so it must be saved somewhere! Does anybody know where?

However, when I use “Send test email” function, e-mail gets properly delivered to my Google for Work mailbox on a same domain (we use mail routing between GfW servers and out local Postfix solution for system users such as Mautic). E-mails are delivered directly from our Postfix server, we DO NOT use GfW SMTP relay. We have properly configured SPF to include both Google IP addresses and our own server addresses. So far, so good, however, if I look into the e-mail, I see following test e-mail gets delivered (as you can see below, “Return-Path: dl-gl-marketing@perlur.cz” is configured instead of sys.app.mautic@perlur.cz, which is the mailbox where Mautic is expecting to get bounce and unsubscribe e-mails. Does anybody have experience with mentioned behavior?

Received: from C105S135VM025.eu.tieto.com (10.34.8.67) by
 C105S135VM016.eu.tieto.com (10.34.8.54) with Microsoft SMTP Server (TLS) id
 15.0.1156.6 via Mailbox Transport; Mon, 29 Feb 2016 12:50:56 +0200
Received: from C105S135VM025.eu.tieto.com (10.34.8.67) by
 C105S135VM025.eu.tieto.com (10.34.8.67) with Microsoft SMTP Server (TLS) id
 15.0.1156.6; Mon, 29 Feb 2016 12:50:56 +0200
Received: from ebb08.tieto.com (10.42.239.172) by mailrelay.tieto.com
 (10.34.8.67) with Microsoft SMTP Server (TLS) id 15.0.1156.6 via Frontend
 Transport; Mon, 29 Feb 2016 12:50:56 +0200
X-AuditID: 0a2aefac-f795c6d000004f61-e8-56d4228f1afa
Authentication-Results: tieto-auth
Received: from glczwe-sp230001.ext.perlur.cz (glczwe-sp230001.ext.perlur.cz [37.157.195.48])
	(using TLS with cipher DHE-RSA-AES256-SHA (256/256 bits))
	(Client did not present a certificate)
	by ebb08.tieto.com (SMTP Mailer) with SMTP id 29.EB.20321.09224D65; Mon, 29 Feb 2016 12:50:56 +0200 (EET)
Received: from www.perlur.cz (glczwe-sp230001.ext.perlur.cz [IPv6:2a02:2b88:2:1::1113:1])
	(Authenticated sender: sys.app.mautic@perlur.cz)
	by glczwe-sp230001.ext.perlur.cz (Postfix) with ESMTPSA id 1867F283F44
	for <ext.marek.stopka@tieto.com>; Mon, 29 Feb 2016 11:50:55 +0100 (CET)
Message-ID: <b1127ce332dbddcc1ff0829cfae7eddb@www.perlur.cz>
Date: Mon, 29 Feb 2016 11:50:55 +0100
Subject: Mautic test email
From: perlur group marketing <dl-gl-marketing@perlur.cz>
To: Marek Stopka <ext.marek.stopka@tieto.com>
MIME-Version: 1.0
X-Brightmail-Tracker: H4sIAAAAAAAAA12TW0gUURjHPTvjetz25Dib63FyK6cbGZldHgxMgiR6MbtKRWWjntzJdVd2
	Zk2NQCuDIsqKkqRM6UIXN6ELFETFVpi95GWxpAyp6E5hDyFU1jnrrs32Mpz5/b9zvv/5/jOQ
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	c9HNS4e659RJw9M+vqxPzovbe2qq9XmO5q/L3b91y8/08zUdg75C7suI+vrGw/4tV45s0OYv
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	/AXeu1ro8AQAAA==
Return-Path: dl-gl-marketing@perlur.cz
X-MS-Exchange-Organization-Network-Message-Id: ce164047-dd4d-4df1-cd89-08d340f633c8
X-MS-Exchange-Organization-AVStamp-Enterprise: 1.0
X-MS-Exchange-Organization-AuthSource: C105S135VM025.eu.tieto.com
X-MS-Exchange-Organization-AuthAs: Anonymous
Content-type: text/plain;
	charset="UTF-8"
Content-transfer-encoding: 7bit

Hi! This is a test email from Mautic. Testing...testing...1...2...3!