Оutgoing mail from the server is not checked for SPF. There is neither pass nor error. Just silence. SPF DKIM DMARC added to DNS, and valid The error is only the PTR of the external service yandex.net, but I will not install them either. But it cannot be the cause. An example of a letter received from the server. HTML: Received: from mxfront9g.mail.yandex.net ([127.0.0.1]) by mxfront9g.mail.yandex.net with LMTP id gEJINozk for <[email protected]>; Thu, 22 Nov 2018 21:47:18 +0300 Received: from ks05.ru (ks05.ru [95.216.36.253]) by mxfront9g.mail.yandex.net (nwsmtp/Yandex) with ESMTPS id xF9meubYN7-lHEGELsv; Thu, 22 Nov 2018 21:47:17 +0300 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client certificate not present) Return-Path: [email protected] X-Yandex-Front: mxfront9g.mail.yandex.net X-Yandex-TimeMark: 1542912437 Authentication-Results: mxfront9g.mail.yandex.net; dkim=pass [email protected] X-Yandex-Spam: 1 Received: from localhost (localhost.localdomain [127.0.0.1]) by ks05.ru (Postfix) with ESMTP id B0B1CF00EFB for <[email protected]>; Thu, 22 Nov 2018 21:47:16 +0300 (MSK) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=dairub.ru; h=date :date:message-id:x-mailer:from:from:subject:subject; s=default; t=1542912434; x=1544726835; bh=frcCV1k9oG9oKj3dpUqdJg1PxRT2RSN/ XKdLCPjaYaY=; b=Vn3IjcFOHx3TEdyoKs9XXYcRerXbDozQoXTzMoLAb6qgHbai 6gUypyYiiYFOWF6g/Awhhjl/6wnmp+GxyTm+1nSdAbui1KLC8sJTfeNgTi0XMijP pecC/LF86LMrl+rD6DF42b4IzQ0kINjIdDmhIEM5LzyxHMDRHxmMKw5d+/Y= X-Virus-Scanned: Debian amavisd-new at ks05.ru Received: from ks05.ru ([127.0.0.1]) by localhost (ks05.ru [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ZTugkeoq1C8O for <[email protected]>; Thu, 22 Nov 2018 21:47:14 +0300 (MSK) Received: by ks05.ru (Postfix, from userid 5013) id E5F33F00F18; Thu, 22 Nov 2018 21:47:14 +0300 (MSK) To: [email protected] Subject: the subject X-PHP-Originating-Script: 0:mail.php From: [email protected] X-Mailer: PHP/5.6.38-2+0~20181015120829.6+stretch~1.gbp567807 Message-Id: <[email protected]> Date: Thu, 22 Nov 2018 21:47:14 +0300 (MSK) X-Yandex-Forward: 107bce4f08bc9bf13e66c15aa5ddb76a How to enable spf and dmarc checking of outgoing mail? Debian9 Ispconfig3 - ap recent version debian 9 (Stretch) with Apache, BIND, Dovecot,
