My Server has 4 IP addresses.
(IPs are for example only) 184.108.40.206 220.127.116.11 18.104.22.168 22.214.171.124
Under IIS, I have a Virtual SMTP Server on 126.96.36.199, on port 25. The virtual server installed there at the start on 188.8.131.52 is disabled.
184.108.40.206 is mapped to my hostname, mailhost.mydomain.com and the rDNS PTR is configured for that as well.
When I send an Email using mailhost.mydomain.com - it works, but it shows up in headers that the email is coming from 220.127.116.11 with no reference to 18.104.22.168 at all.