==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release):  0.9.9 MARIADB edition
- Deployed with iRedMail Easy or the downloadable installer?
- Linux/BSD distribution name and version: Debian
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro?: iRedAdmin-Pro
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

hello Zhang,

A few of my customers are getting a Mailer-daemon bounce message error while sending a specific email. Error message is given below.

I have gone through the forums and googled, but not sure on the correct solution.

Help required urgently please

######################
-----Original Message-----
From: Mail Delivery System <MAILER-DAEMON@ns1.MyHostName.net>
Sent: 21 April 2020 17:07
To: user@MyCustomerDomain.com
Subject: Undelivered Mail Returned to Sender

This is the mail system at host ns1.MyHostName.net.
I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below.
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
<user@abc.com>: SMTPUTF8 is required, but was not offered by
host 127.0.0.1[127.0.0.1]

<user@pqr.com>: SMTPUTF8 is required, but was not offered by
host 127.0.0.1[127.0.0.1]

<user@xyz.com>: SMTPUTF8 is required, but was not offered
by host 127.0.0.1[127.0.0.1]

######################

thanks
rajesh