Since xeams listens on port 25, it's the SMTP server now, so you should configure xeams to not be an open relay, not Postfix or iRedMail. So, i think you should ask support from xeams instead.
Thanks for the response.
maybe i did not explain myself properly
I am looking at this article explaining the error i am getting
http://www.xeams.com/openrelaytest.htm
Problem description
When you use the SMTP Proxy server in Xeams, the actual user and domain authentication is done by your actual server(iredmail). Meaning when an incoming message comes for James@YourCompany.com, its your actual SMTP server(iredmail) that checks if it can accept email for this user.
The actual SMTP server (iredmail) also thinks that the email is coming from the IP address where Xeams is running. It is no idea that there is a Proxy server in the middle.
"Solution::
You must configure your actual SMTP(which is iredmail) server, such MS Exchange, NOT to accept relay from the IP address where Xeams is running. Since every email received by your actual SMTP server appears to have come from Xeams, allowing relaying from this IP address opens up your email system to accept relayed messages from the Internet. "