I have a mail server, postfix for SMTP and Dovecot for IMAP, both require authentication. I just received an email from MY address, but coming from an other SMTP server. And of course, in message source, I can see this server from which it was sent, but not the user who did that, only its machine name "debian.world".
How can I protect myself against this ? Because it basically means that the guy can send emails to anyone using my address, and I don't think random people will check message source to check from which SMTP it comes from. Can i configure something on my server which will check authencicity of a sender ? Or should I write a whole script on my own ?
One more question : how am i supposed to read this :
Return-Path: <email@example.com> Delivered-To: <myOTHERaddress@server.com> Received: from my.imap.myserver.com by my.imap.myserver.com (Dovecot) with LMTP id aEG5JBhePlnSDgAAz5VDmw for <myOTHERaddress@server.com>; Mon, 12 Jun 2017 11:25:44 +0200 Received: from smtp25.services.sfr.fr (smtp25.services.sfr.fr [126.96.36.199]) by my.smtp.myserver.com (Postfix) with ESMTPS id C693C3F0FE for <myOTHERaddress@server.com>; Mon, 12 Jun 2017 11:25:43 +0200 (CEST) Received: from debian.world (188.8.131.52.rev.sfr.net [184.108.40.206]) by msfrf2635.sfr.fr (SMTP Server) with ESMTP id 055631C00081D for <myOTHERaddress@server.com>; Mon, 12 Jun 2017 11:25:28 +0200 (CEST) Received: from debian.world (220.127.116.11.rev.sfr.net [18.104.22.168]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-SHA256 (128/128 bits)) (No client certificate requested) by msfrf2635.sfr.fr (SMTP Server) with ESMTPS for <myOTHERaddress@server.com>; Mon, 12 Jun 2017 11:25:22 +0200 (CEST) Message-ID: <953862.473459111-sendEmail@debian> From: ME <firstname.lastname@example.org> To: "myOTHERaddress@server.com" <myOTHERaddress@server.com> Subject: etc...
(I've received a mail from email@example.com on my address myOTHERaddress@server.com, but he also sent me a mail from firstname.lastname@example.org for example)
What does that mean ? The email comes from smtp25.services.sfr.fr, but what is msfrf2635.sfr.fr ? Why is there 3 involved SMTP ? I'd like to understand this please...
Thank you fellows.
PS: I changed some crucial informations because I know the guy who did that, and I don't want him to have troubles with his servers. The msfrf2635.sfr.fr is unchanged though.