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

I have installed iredmail server in a vps. when i am sending an email to user@hotmail.com , the error shows.please give me any solutions  for the issue.

This is the mail system at host hello.technaureus.com.

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

<sameer_rm90@hotmail.com>: host
   hotmail-com.olc.protection.outlook.com[104.47.18.225] said: 550 5.7.1
   Unfortunately, messages from [143.110.181.46] weren't sent. Please contact
   your Internet service provider since part of their network is on our block
   list (S3140). You can also refer your provider to
   http://mail.live.com/mail/troubleshooting.aspx#errors.
   [VI1EUR06FT064.eop-eur06.prod.protection.outlook.com] (in reply to MAIL
   FROM command)
Reporting-MTA: dns; hello.technaureus.com
X-Postfix-Queue-ID: 4CRWjQ3SClz5tkM
X-Postfix-Sender: rfc822; support@technaureus.com
Arrival-Date: Thu,  5 Nov 2020 05:07:22 +0000 (UTC)

Final-Recipient: rfc822; sameer_rm90@hotmail.com
Original-Recipient: rfc822;sameer_rm90@hotmail.com
Action: failed
Status: 5.7.1
Remote-MTA: dns; hotmail-com.olc.protection.outlook.com
Diagnostic-Code: smtp; 550 5.7.1 Unfortunately, messages from [143.110.181.46]
   weren't sent. Please contact your Internet service provider since part of
   their network is on our block list (S3140). You can also refer your
   provider to http://mail.live.com/mail/troubleshooting.aspx#errors.
   [VI1EUR06FT064.eop-eur06.prod.protection.outlook.com]