This is what senders receive as notification message regarding the error:
This is the mail system at host box.my_miab.com.
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# THIS IS A WARNING ONLY. YOU DO NOT NEED TO RESEND YOUR MESSAGE. #
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Your message could not be delivered for more than 3 hour(s).
It will be retried until it is 2 day(s) old.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The mail system
<receiver@gmail.com>: server unavailable or unable to receive mail
Reporting-MTA: dns; box.my_miab.com
X-Postfix-Queue-ID: 5D716800E7
X-Postfix-Sender: rfc822; sender@my_miab.com
Arrival-Date: Thu, 28 Nov 2024 00:01:23 +0900 (JST)
Final-Recipient: rfc822; receiver@gmail.com
Original-Recipient: rfc822;receiver@gmail.com
Action: delayed
Status: 4.3.0
Diagnostic-Code: X-Postfix; server unavailable or unable to receive mail
Will-Retry-Until: Sat, 30 Nov 2024 00:01:23 +0900 (JST)
Return-Path: <sender@my_miab.com>
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=my_miab.com; s=mail;
t=1732719683; bh=g3zLYH4xKxcPrHOD18z9YfpQcnk/GaJedfustWU5uGs=;
h=Date:From:To:Subject:From;
b=HQMkrfUcSHHjNCVwCM7vM2kPL9jiIpzG8D7y2yz9ZRO2vQwroNCLTKpNNoZ8JVnyJ
9XvvhVhUepWTUi+uYdj7ugirYNOMBy6mYKTh2d1iacKLt+LyNPiK3qBT7b0BUHhSp6
Xoi742h/4g2x2tw9T9zC5oCWqjJko1ruy4vbuBTD7Rf6E1Jx7NyeWvf1Km1lDCkEqR
YZHUtHjmgi3EYkarQTN1bb73wxbaqTJXDaZaY3HYVA6MTM7SwmzIn+e3BmYzCIjiwA
n3ANXQwq95i0j8RRtoN2FnuOOiglk5UvVDmqtg+VigYwcewSGXZIUPYuBq5ASAbxB+
Zd/tXfMpTQ5Rw==
Received: from authenticated-user (box.my_miab.com [xxx.xxx.xxx.xxx])
(using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits)
key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256)
(No client certificate requested)
by box.my_miab.com (Postfix) with ESMTPSA id 5D716800E7
for <receiver@gmail.com>; Thu, 28 Nov 2024 00:01:23 +0900 (JST)
Message-ID: <dfe9a53c-686c-4e45-ab4a-2c2a090163f1@my_miab.com>
Date: Thu, 28 Nov 2024 00:01:20 +0900
MIME-Version: 1.0
From: =?UTF-8?B?44Os44OI44O744OQ44Km44Og44Ks44Or44OI44OK44O877yI5ZCI5ZCM5Lya?=
=?UTF-8?B?56S+44Ks44Os44ON77yJ?= <sender@my_miab.com>
Content-Language: en-GB
To: "receiver@gmail.com" <receiver@gmail.com>
Subject: test
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit