==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 1.5.1
- Deployed with iRedMail Easy or the downloadable installer? Installer
- Linux/BSD distribution name and version: Ubuntu server 20.04.3
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): Mariadb
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? No
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

Dear Sirs, I want to be able to receive emails from a domain like *dei.com.gr e.x. EDGE16A.dei.com.gr
EDGE16B.dei.com.gr  etc
The above servers does not resolve to IP unfortunately. What is necessary to do for email reception from them?
Please see the error from the log:

Mar 10 10:41:03 mx postfix/smtpd[3367238]: NOQUEUE: reject: RCPT from smgout.dei.com.gr[62.169.201.50]: 450 4.7.1 <EDGE16A.dei.com.gr>: Helo command rejected: Host not found; from=<noreply@dei.gr> to=<caesar@openforall.com> proto=ESMTP helo=<EDGE16A.dei.com.gr>
Mar 10 10:41:03 mx postfix/smtpd[3367238]: disconnect from smgout.dei.com.gr[62.169.201.50] ehlo=2 starttls=1 mail=1 rcpt=0/1 quit=1 commands=5/6

Please give me advice or solution.

Thanks and Best Regards,
Mike Kranidis