My Server has 4 IP addresses.
(IPs are for example only) 220.127.116.11 18.104.22.168 22.214.171.124 126.96.36.199
Under IIS, I have a Virtual SMTP Server on 188.8.131.52, on port 25. The virtual server installed there at the start on 184.108.40.206 is disabled.
220.127.116.11 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 18.104.22.168 with no reference to 22.214.171.124 at all.