============ REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 0.9.8
- Linux/BSD distribution name and version: CentOS 7
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MariaDB
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? Yes
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

I've had a few complaints from customers who had their contacts report bounces when emailing them.  In the maillog is was obvious that those contacts have their mail server configured to advertise themselves with a name that wasn't create in their DNS.  The lof file shows this:

Jun 24 04:42:36 email postfix/postscreen[11841]: CONNECT from [213.120.130.65]:36144 to [aaa.bbb.ccc.ddd]:25
Jun 24 04:42:36 email postfix/postscreen[11841]: PASS OLD [213.120.130.65]:36144
Jun 24 04:42:36 email postfix/smtpd[11844]: connect from mail.clark-drain.com[213.120.130.65]
Jun 24 04:42:36 email postfix/smtpd[11844]: NOQUEUE: reject: RCPT from mail.clark-drain.com[213.120.130.65]: 450 4.7.1 <barracuda.clark-drain.com>: Helo command rejected: Host not found; from=<btv1==713843054a7==abcde@clark-drain.com> to=<xxx@yyy.zzz> proto=ESMTP helo=<barracuda.clark-drain.com>
Jun 24 04:42:37 email postfix/smtpd[11844]: disconnect from mail.clark-drain.com[213.120.130.65]

As you can see it gets rejected with Helo command rejected: Host not found;

If it was only 1 contact I could circumvent it by putting the host name in the hosts file, but there seem to be more and more.  I would like to protect the server against spam as much as possible but it seems like this is preventing a lot of people from emailing my customers as nobody seems to have a clue how to configure their email server.

For one of the contacts I told them it was a problem with their server name not existing and they came back with "the problem is on your side".  I could argue a long time but in the end, the people who installed and configured their server don't have a clue and my customer won't be happy

I can take off the protection but I prefer not to if not necessary.  What are your thoughts on this?