==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 1.6.2
- Deployed with iRedMail Easy or the downloadable installer?
- Linux/BSD distribution name and version: Ubuntu 20.04 server
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? not pro
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

Hi, i'm getting an error sending mail to a specific address.
Not error with gmail.com, outlook.com or something else...

I report my error:

--------------

This is the mail system at host xxx.mydomain.xx

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@domain.com>: host smtp-avas.seeweb.it[IP] said:
    550 5.7.1 Blocked due to message content - please contact
    postmaster@seeweb.it (in reply to end of DATA command)
Reporting-MTA: dns; email.acetest.it
X-Postfix-Queue-ID: 4QNJkC1kvQzRmJd
X-Postfix-Sender: rfc822; user@mydomain.xx
Arrival-Date: Fri, 19 May 2023 20:44:51 +0000 (UTC)

Final-Recipient: rfc822; user@domain.xx
Original-Recipient: rfc822;user@domain.xx
Action: failed
Status: 5.7.1
Remote-MTA: dns; smtp-avas.seeweb.it
Diagnostic-Code: smtp; 550 5.7.1 Blocked due to message content - please
    contact postmaster@seeweb.it
---------------

I could resolve editing something in DNS or iredmail or not?
Thank you.