==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 1.6.5
- Deployed with iRedMail Easy or the downloadable installer? downloadable
- Linux/BSD distribution name and version: Ubuntu 22.04
- 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.
====

I've been getting the following bounce error:

    450 4.7.1 <mta.cardcommunication.capitalone.com>: Helo command rejected: Host not found; from=<bounce-50_HTML-398169449-839280-518004831-4078@bounce-cardcommunication.capitalone.com> to=<email@server.address> proto=ESMTP helo=<mta.cardcommunication.capitalone.com> (total: 36)

I would like to allow this email through.  I've had another bank send email from non-existent addresses (e.g. noreply@statements.bank.com)

In /etc/postfix/header_checks I have the below lines:

/^From:.*bounce-cardcommunication.capitalone.com/ OK
/mta.cardcommunication.capitalone.com/ OK

I have other lines in header_checks that work.  I then issue the commands

$postmap header_checks 

and

$postfix reload

The emails are still being rejected. 

Two questions -
1) How can I whitelist these to be accepted by the server?
2) Is there a good reference for the header_checks syntax? I've tried looking but I haven't found a good guide other than piecemeal examples.

Thanks.