Otdfbt

Postfix users receive spam pretending to be sent from their accounts.

in main.cf I have put:

smtpd_sender_login_maps = mysql:/etc/postfix/mysql_virtual_mailbox_maps.cf,
 mysql:/etc/postfix/mysql_virtual_alias_maps.cf

smtpd_sender_restrictions = permit_mynetworks,
 permit_sasl_authenticated,
 reject_sender_login_mismatch,

I also have extensive rbl and other spam checks in main.cf which work, but this slips through it anyway (see msg source)
If I test it from my other server

root@othermail:~# mail -s test1 -a "From: user1@mydomain.tld" user1@mydomain.tld < /dev/null

The message gets rejected in log with

NOQUEUE: reject: RCPT from myother.server.tld[192.168.7.229]: 553 5.7.1 <user1@mydomain.tld>: Sender address rejected: not logged in; from=<user1@mydomain.tld> to=<user1@mydomain.tld>

I have DKIM which works and validates. IN main.cf

milter_default_action = accept
milter_protocol = 6
smtpd_milters = local:opendkim/opendkim.sock
non_smtpd_milters = local:opendkim/opendkim.sock

But the spamers somehow trick it by using DKIM? or other means.
Somehow after milter OpenDKIM there are no sender_login_mismatch checks. Should I install amavis? It seems so trivial to block spam which pretend to be sent as a spoofed message from oneself but yet I can't block it. Any suggestions? Thanks.

Message source looks like this:

Return-Path: <seisi@kousaikan.com>
X-Original-To: user1@mydomain.tld
Delivered-To: user1@mydomain.tld
Received: from mail.mydomain.tld (localhost [127.0.0.1])
 by mail.mydomain.tld (Postfix) with ESMTP id 73A553008B0
 for <user1@mydomain.tld>; Fri, 5 Apr 2019 17:16:49 +0300 (EEST)
DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=mydomain.tld; s=201902;
 t=1554473809; bh=MjZrE+ZNsa79fhqHRgjB41LtBj2nZeIT/I8ZyQz4lvI=;
 h=Date:Subject:To:From:List-Help:From;
 b=ajW/fpbQ9R/wu2ztE6OJecLpcUqvqENooIo6PW1V5GU0oAc/VqhvxuGPIc89t9n49
 6pcXOw4knfTpp9lwoaHqUJ8lM2KpesQTSgLHzvfC74u8wi9CB6+cHpS42rT35bW5wx
 LvdO7mLT9GEhrPAVeoI21yk2pCAEhBQaXLAFDsmY=
Received: from orange-leopard-671e4d6e5ce74ab6.znlc.jp (orange-leopard-671e4d6e5ce74ab6.znlc.jp [154.34.23.45])
 by mail.mydomain.tld (Postfix) with ESMTPS id 36A99300704
 for <user1@mydomain.tld>; Fri, 5 Apr 2019 17:16:47 +0300 (EEST)
Received: from [corporativo.static.gvt.net.br] (170.83.215.114-static.host.megalink.net.br [170.83.215.114])
 by orange-leopard-671e4d6e5ce74ab6.znlc.jp (Postfix) with ESMTPSA id 1C8A2BDEE
 for <user1@mydomain.tld>; Fri, 5 Apr 2019 22:12:20 +0900 (JST)
Date: Fri, 5 Apr 2019 15:12:18 +0200
Abuse-Reports-To: <abuse@mail.kousaikan.com>
X-Complaints-To: abuse@mail.kousaikan.com
Subject: [SPAM] user1
Message-ID: <j2w06zpo-msrn-unjm-z17p-4ld3vmq62lf7@mlcp.tzzu>
To: user1@mydomain.tld
Content-Type: multipart/related;
 boundary="--_com.android.email_86436944273605"
MIME-Version: 1.0
X-Mailer: Summer Cart 4.0
From: <user1@mydomain.tld>
User-Agent: Roundcube Webmail/0.6
List-Help: 
 <http://www.kousaikan.com/lists/?p=preferences&uid=7oivc5xd99g9y6j9mcp0iztxw78pnnhu>
X-Antivirus: Dr.Web (R) for Unix mail servers drweb plugin ver.6.0.2.8
X-Antivirus-Code: 0x100000
X-Drweb-SpamState: yes
X-Drweb-SpamScore: 315
X-DrWeb-SpamReason: gggruggvucftvghtrhhoucdtuddrgeduuddrtdeiucetufdoteggodetrfcurfhrohhfihhlvgemuceonhhonhgvqeenuceurghilhhouhhtmecupfdsteenucgoteeftdduqddtudculdduhedmnegoufhprghmsghotheuvfevqdfggedutddqvdekucdlfedttddm
X-AV-Checked: ClamAV using ClamSMTP

Log file:

Apr 5 17:16:45 mydomain.tld postfix/smtpd[11659]: connect from orange-leopard-671e4d6e5ce74ab6.znlc.jp[154.34.23.45]
Apr 5 17:16:46 mydomain.tld postfix/smtpd[11659]: Anonymous TLS connection established from orange-leopard-671e4d6e5ce74ab6.znlc.jp[154.34.23.45]: TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)
Apr 5 17:16:47 mydomain.tld postfix/smtpd[11659]: 36A99300704: client=orange-leopard-671e4d6e5ce74ab6.znlc.jp[154.34.23.45]
Apr 5 17:16:47 mydomain.tld postfix/cleanup[11826]: 36A99300704: message-id=<j2w06zpo-msrn-unjm-z17p-4ld3vmq62lf7@mlcp.tzzu>
Apr 5 17:16:49 mydomain.tld opendkim[539]: 36A99300704: orange-leopard-671e4d6e5ce74ab6.znlc.jp [154.34.23.45] not internal
Apr 5 17:16:49 mydomain.tld opendkim[539]: 36A99300704: not authenticated
Apr 5 17:16:49 mydomain.tld opendkim[539]: 36A99300704: no signature data
Apr 5 17:16:49 mydomain.tld postfix/qmgr[11471]: 36A99300704: from=<seisi@kousaikan.com>, size=257396, nrcpt=1 (queue active)
Apr 5 17:16:49 mydomain.tld clamsmtpd: 1009A6: accepted connection from: 127.0.0.1
Apr 5 17:16:49 mydomain.tld postfix/smtpd[11829]: connect from localhost[127.0.0.1]
Apr 5 17:16:49 mydomain.tld postfix/smtpd[11829]: 73A553008B0: client=localhost[127.0.0.1], orig_queue_id=36A99300704, orig_client=orange-leopard-671e4d6e5ce74ab6.znlc.jp[154.34.23.45]
Apr 5 17:16:49 mydomain.tld postfix/smtpd[11659]: disconnect from orange-leopard-671e4d6e5ce74ab6.znlc.jp[154.34.23.45] ehlo=2 starttls=1 mail=1 rcpt=1 data=1 quit=1 commands=7
Apr 5 17:16:49 mydomain.tld postfix/cleanup[11826]: 73A553008B0: message-id=<j2w06zpo-msrn-unjm-z17p-4ld3vmq62lf7@mlcp.tzzu>
Apr 5 17:16:49 mydomain.tld postfix/qmgr[11471]: 73A553008B0: from=<seisi@kousaikan.com>, size=257617, nrcpt=1 (queue active)
Apr 5 17:16:49 mydomain.tld postfix/smtp[11827]: 36A99300704: to=<user1@mydomain.tld>, relay=127.0.0.1[127.0.0.1]:10026, delay=2.9, delays=2.3/0.01/0.06/0.51, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as 73A553008B0)
Apr 5 17:16:49 mydomain.tld postfix/qmgr[11471]: 36A99300704: removed
Apr 5 17:16:49 mydomain.tld clamsmtpd: 1009A6: from=seisi@kousaikan.com, to=user1@mydomain.tld, status=CLEAN
Apr 5 17:16:49 mydomain.tld postfix/smtpd[11829]: disconnect from localhost[127.0.0.1] ehlo=1 xforward=2 mail=1 rcpt=1 data=1 quit=1 commands=7
Apr 5 17:16:50 mydomain.tld postfix/virtual[11832]: 73A553008B0: to=<user1@mydomain.tld>, relay=virtual, delay=0.58, delays=0.51/0.01/0/0.06, dsn=2.0.0, status=sent (delivered to maildir)
Apr 5 17:16:50 mydomain.tld postfix/qmgr[11471]: 73A553008B0: removed